Oh man that's a lot of changes.

API.md

@@ -0,0 +1,102 @@
+# Overview
+
+COMS uses a WebSocket API to communicate with its clients in JSON. In general,
+packets sent to all clients end in `_evt` and packets sent in reply to a client
+action end in `_ack`. Beyond that there isn't really a system.
+
+A packet takes this general form:
+
+```json
+{
+  "type": "<PacketType>",
+  "data": {...}
+}
+```
+
+# Data types
+
+## Packet
+
+**Type:**
+```C
+struct {
+    PacketType type;
+    Any data;
+}
+```
+
+A packet.
+
+## PacketType
+
+**Type:**
+```C
+enum {
+    join,
+    welcome,
+    join_evt,
+    msg,
+    msg_evt,
+    name,
+    name_evt,
+    ping,
+    pong,
+    msg_ack,
+    name_ack,
+    leave_evt,
+    bad,
+}
+```
+
+The type a Packet may assume.
+
+## UserID
+
+**Type:** `uint64_t`
+
+Uniquely identifies a user.
+
+## Name
+
+**Type:** `char[16]`
+
+A name of a user.
+
+## UserData
+
+**Type:**
+```C
+struct {
+  UserID id;
+  Name name;
+}
+```
+
+A user.
+
+## MsgID
+
+**Type:** `uint64_t`
+
+Uniquely identifies a message.
+
+## MsgContent
+
+**Type:** `char[1024]`
+
+The content of a message.
+
+## MsgData
+
+**Type:**
+```C
+struct {
+    MsgID id;
+    UserData author;
+    MsgID parent;
+    MsgContent content;
+    time_t timestamp;
+}
+```
+
+A message.

client/public/app.js

@@ -27,7 +27,7 @@ document.addEventListener("DOMContentLoaded", () => {
   inputContainer.style.display = "flex";
 
   const defaultName = "Anon";
-  const MAX_NAME_LEN = 31;
+  const MAX_NAME_LEN = 15; // server limit is NAME_MAX_LENGTH-1 (15 chars)
 
   const { socket, sendMessage, sendName } = initWebSocket(
     defaultName,
@@ -88,8 +88,8 @@ document.addEventListener("DOMContentLoaded", () => {
   chat.addEventListener("click", (e) => {
     const msgDiv = e.target.closest(".msg");
     if (!msgDiv) return;
-    const id = Number(msgDiv.dataset.id);
+    const id = msgDiv.dataset.id;
-    if (!isFinite(id)) return;
+    if (!id) return;
     const threads = getThreads();
     const author = threads.get(id)?.username;
     setReplyTo(id);
@@ -124,9 +124,7 @@ document.addEventListener("DOMContentLoaded", () => {
     if (e.key === "ArrowDown" || e.key === "ArrowUp") {
       const msgs = Array.from(chat.querySelectorAll("div.msg"));
       if (!msgs.length) return;
-      let idx = msgs.findIndex(
+      let idx = msgs.findIndex((div) => div.dataset.id === getFocused());
-        (div) => Number(div.dataset.id) === getFocused(),
-      );
       if (idx === -1) {
         idx = e.key === "ArrowDown" ? -1 : msgs.length;
       }
@@ -134,7 +132,7 @@ document.addEventListener("DOMContentLoaded", () => {
         e.key === "ArrowDown"
           ? Math.min(msgs.length - 1, idx + 1)
           : Math.max(0, idx - 1);
-      const newId = Number(msgs[idx].dataset.id);
+      const newId = msgs[idx].dataset.id;
       setFocused(newId);
       setReplyTo(newId); // Move input box under focused message.
       const threads = getThreads();

client/public/data.js

@@ -1,7 +1,7 @@
 // coms/client/public/data.js
 // Data module: holds the in‐memory threads, notices and reply state
 
-// Map of all messages and notices by ID
+// Map of all messages and notices by ID (string IDs)
 // Client’s own session ID
 let myId = null;
 const threads = new Map();
@@ -9,28 +9,28 @@ const threads = new Map();
 // Map of connected users by unique ID
 const users = new Map();
 
-// Ordered list of root‐level IDs (messages and notices)
+// Ordered list of root‐level IDs (messages and notices, stored as strings)
 const rootIds = [];
 
 // Negative counter to generate unique IDs for notices
 let noticeCounter = -1;
 
-// ID of the message we’re currently replying to (or null)
+// ID of the message we’re currently replying to (string or null)
 let replyTo = null;
 
-// ID of the message currently focused for navigation (or null)
+// ID of the message currently focused for navigation (string or null)
 let focusedId = null;
 
 /**
  * Set the focused message ID (or null to clear).
- * @param {number|null} id
+ * @param {string|null} id
  */
 function setFocused(id) {
   focusedId = id;
 }
 /**
  * Get the currently focused message ID.
- * @returns {number|null}
+ * @returns {string|null}
  */
 function getFocused() {
   return focusedId;
@@ -46,7 +46,7 @@ function clearFocused() {
 
 /**
  * Register a user with their unique ID.
- * @param {number} id
+ * @param {string} id
  * @param {string} name
  */
 function addUser(id, name) {
@@ -55,7 +55,7 @@ function addUser(id, name) {
 
 /**
  * Remove a user by their ID.
- * @param {number} id
+ * @param {string} id
  */
 function removeUser(id) {
   users.delete(id);
@@ -63,7 +63,7 @@ function removeUser(id) {
 
 /**
  * Update a user’s name.
- * @param {number} id
+ * @param {string} id
  * @param {string} name
  */
 function updateUser(id, name) {
@@ -72,7 +72,7 @@ function updateUser(id, name) {
 
 /**
  * Get a list of {id, name} objects for all users.
- * @returns {{id:number, name:string}[]}
+ * @returns {{id:string, name:string}[]}
  */
 function getUsers() {
   return Array.from(users.entries()).map(([id, name]) => ({ id, name }));
@@ -95,14 +95,31 @@ function getGroupedUsers() {
 
 /**
  * Add a new chat message to the thread structure.
- * @param {{id: number, username: string, content: string, ts: number, parent?: number}} msg
+ * @param {{id: string|number, username: string, content: string, ts: number, parent?: string|number|null, authorId?: string|number|null}} msg
  */
-function addMessage({ id, username, content, ts, parent = null }) {
+function addMessage({
-  threads.set(id, { id, username, content, ts, parent, children: [] });
+  id,
-  if (parent !== null && threads.has(parent)) {
+  username,
-    threads.get(parent).children.push(id);
+  content,
+  ts,
+  parent = null,
+  authorId = null,
+}) {
+  const sid = String(id);
+  const sparent = parent === null ? null : String(parent);
+  threads.set(sid, {
+    id: sid,
+    username,
+    authorId: authorId === null ? null : String(authorId),
+    content,
+    ts,
+    parent: sparent,
+    children: [],
+  });
+  if (sparent !== null && threads.has(sparent)) {
+    threads.get(sparent).children.push(sid);
   } else {
-    rootIds.push(id);
+    rootIds.push(sid);
   }
 }
 
@@ -112,7 +129,7 @@ function addMessage({ id, username, content, ts, parent = null }) {
  */
 function addNotice(content) {
   const ts = Math.floor(Date.now() / 1000);
-  const id = noticeCounter--;
+  const id = String(noticeCounter--);
   threads.set(id, {
     id,
     username: "",
@@ -132,40 +149,41 @@ function clearData() {
   rootIds.length = 0;
   noticeCounter = -1;
   replyTo = null;
+  users.clear();
 }
 
-/** @returns {Map<number,object>} The threads map. */
+/** @returns {Map<string,object>} The threads map. */
 function getThreads() {
   return threads;
 }
 
-/** @returns {number[]} The ordered list of root‐level IDs. */
+/** @returns {string[]} The ordered list of root‐level IDs. */
 function getRootIds() {
   return rootIds;
 }
 
 /**
  * Set this client’s own session ID.
- * @param {number} id
+ * @param {string|number} id
  */
 function setMyId(id) {
-  myId = id;
+  myId = String(id);
 }
 
 /**
  * Get this client’s own session ID.
- * @returns {number|null}
+ * @returns {string|null}
  */
 function getMyId() {
   return myId;
 }
 
-/** @returns {number|null} The current reply‐to ID. */
+/** @returns {string|null} The current reply‐to ID. */
 function getReplyTo() {
   return replyTo;
 }
 
-/** @param {number|null} id — Set the current reply‐to ID. */
+/** @param {string|null} id — Set the current reply‐to ID. */
 function setReplyTo(id) {
   replyTo = id;
 }

client/public/wsModule.js

@@ -9,6 +9,7 @@ import {
   addNotice,
   getReplyTo,
   addUser,
+  removeUser,
   updateUser,
   getGroupedUsers,
   setMyId,
@@ -39,8 +40,7 @@ export function initWebSocket(username, chatEl, inputContainer, usersListEl) {
 
   socket.onopen = () => {
     // Announce join.
-    socket.send(JSON.stringify({ type: "join", data: { username } }));
+    socket.send(JSON.stringify({ type: "join", data: { name: username } }));
-    //addNotice(`Connected as <span class="name">${username}</span>`);
     renderChat(chatEl, inputContainer);
   };
 
@@ -48,32 +48,60 @@ export function initWebSocket(username, chatEl, inputContainer, usersListEl) {
     const packet = JSON.parse(event.data);
     switch (packet.type) {
       case "welcome": {
-        // Initial user list.
+        // Initial handshake. Populate ids, online list, and history if provided.
-        const myId = packet.data.you;
         clearData();
-        setMyId(myId);
+        const { id, online = [], history = [] } = packet.data;
-        const users = packet.data.users || [];
+        setMyId(String(id));
-        users.forEach(({ id, username }) => addUser(id, username));
+        online.forEach(({ id: uid, name }) => addUser(String(uid), name));
+        history.forEach((m) => {
+          addMessage({
+            id: String(m.id),
+            username: m.author?.name || "Anon",
+            authorId: m.author?.id ? String(m.author.id) : null,
+            content: m.content,
+            ts: m.timestamp,
+            parent:
+              m.parent === null || m.parent === undefined || m.parent === "-1"
+                ? null
+                : String(m.parent),
+          });
+        });
         const groups = getGroupedUsers();
-        usersListEl.innerHTML = "Online: " + groups.join(", ");
+        usersListEl.innerHTML = groups.length
-        //addNotice(`<i>Users online: ${groups.join(", ")}</i>`);
+          ? "Online: " + groups.join(", ")
+          : "Online: ?";
         break;
       }
-      case "join-event": {
+      case "join_evt": {
         // A new user joined.
-        const { id, username } = packet.data;
+        const { id, name } = packet.data;
-        addUser(id, username);
+        addUser(String(id), name);
         addNotice(
-          `<span class="name">${new Option(username).innerHTML}</span> joined.`,
+          `<span class="name">${new Option(name).innerHTML}</span> joined.`,
         );
         const groups = getGroupedUsers();
         usersListEl.innerHTML = "Online: " + groups.join(", ");
         break;
       }
-      case "name-event": {
+      case "leave_evt": {
+        const { id, name } = packet.data;
+        const sid = String(id);
+        const lastName = users.get(sid) || name;
+        addNotice(
+          `<span class="name">${new Option(lastName).innerHTML}</span> left.`,
+        );
+        removeUser(sid);
+        const groups = getGroupedUsers();
+        usersListEl.innerHTML = "Online: " + groups.join(", ");
+        break;
+      }
+      case "name_evt": {
         // A user changed name.
-        const { id, new: newName, old: oldName } = packet.data;
+        const {
-        updateUser(id, newName);
+          user: { id, name: oldName },
+          new_name: newName,
+        } = packet.data;
+        updateUser(String(id), newName);
         addNotice(
           `<span class="name">${new Option(oldName).innerHTML}</span> changed name to <span class="name">${new Option(newName).innerHTML}</span>`,
         );
@@ -81,19 +109,53 @@ export function initWebSocket(username, chatEl, inputContainer, usersListEl) {
         usersListEl.innerHTML = "Online: " + groups.join(", ");
         break;
       }
-      case "msg-event": {
+      case "msg_evt": {
         // A chat message arrived.
-        const { id, username: u, content, ts, parent } = packet.data;
+        const { id, author, content, parent, timestamp } = packet.data;
-        addMessage({ id, username: u, content, ts, parent });
+        const username = author?.name || "Anon";
+        const ts = timestamp || Math.floor(Date.now() / 1000);
+        if (author?.id) addUser(String(author.id), username);
+        addMessage({
+          id: String(id),
+          username,
+          authorId: author?.id ? String(author.id) : null,
+          content,
+          ts,
+          parent:
+            parent === null || parent === undefined || parent === "-1"
+              ? null
+              : String(parent),
+        });
         break;
       }
-      case "msg-ack": {
+      case "msg_ack": {
-        const { id } = packet.data;
+        const { status, id } = packet.data;
-        if (getReplyTo() === null) {
+        if (status !== "success") {
-          setFocused(id);
+          addNotice(
-          setReplyTo(id);
+            `<span class="err">Message failed: ${new Option(status).innerHTML}</span>`,
+          );
+        } else if (id) {
+          const replyTarget = getReplyTo();
+          if (replyTarget === null) {
+            const sid = String(id);
+            setFocused(sid);
+            setReplyTo(sid);
+          }
         }
-        renderChat(chatEl, inputContainer);
+        break;
+      }
+      case "name_ack": {
+        const { status, name } = packet.data;
+        if (status !== "success") {
+          addNotice(
+            `<span class="err">Name change failed: ${new Option(status).innerHTML}</span>`,
+          );
+        }
+        break;
+      }
+      case "ping": {
+        const ts = packet.data?.ts ?? Math.floor(Date.now() / 1000);
+        socket.send(JSON.stringify({ type: "pong", data: { ts } }));
         break;
       }
       default:
@@ -122,7 +184,12 @@ export function initWebSocket(username, chatEl, inputContainer, usersListEl) {
    */
   function sendMessage(content) {
     const parent = getReplyTo();
-    socket.send(JSON.stringify({ type: "msg", data: { content, parent } }));
+    socket.send(
+      JSON.stringify({
+        type: "msg",
+        data: { content, parent: parent == null ? -1 : parent },
+      }),
+    );
   }
 
   /**
@@ -130,7 +197,7 @@ export function initWebSocket(username, chatEl, inputContainer, usersListEl) {
    * @param {string} username - The new username to set.
    */
   function sendName(username) {
-    socket.send(JSON.stringify({ type: "name", data: { username } }));
+    socket.send(JSON.stringify({ type: "name", data: { name: username } }));
   }
 
   return { socket, sendMessage, sendName };

server/src/api.c

@@ -1,17 +1,22 @@
 #include "include/api.h"
 
+#include <inttypes.h>
 #include <stdlib.h>
 #include <string.h>
+#include <yyjson.h>
 
 static const char* packet_type_strings[] = {
     [PACKET_TYPE_JOIN] = "join",         [PACKET_TYPE_WELCOME] = "welcome",
     [PACKET_TYPE_JOIN_EVT] = "join_evt", [PACKET_TYPE_MSG] = "msg",
-    [PACKET_TYPE_MSG_EVT] = "msg_evt",
+    [PACKET_TYPE_MSG_EVT] = "msg_evt",   [PACKET_TYPE_NAME] = "name",
+    [PACKET_TYPE_NAME_EVT] = "name_evt", [PACKET_TYPE_LEAVE_EVT] = "leave_evt",
+    [PACKET_TYPE_PING] = "ping",         [PACKET_TYPE_PONG] = "pong",
+    [PACKET_TYPE_MSG_ACK] = "msg_ack",   [PACKET_TYPE_NAME_ACK] = "name_ack",
 
 };
 
 PacketType packet_type_parse(const char* type) {
-    for (int i = 0; i < PACKET_TYPE_MAX; i++)
+    for (int i = 0; i <= PACKET_TYPE_MAX; i++)
         if (!strcmp(type, packet_type_strings[i])) return (PacketType)i;
 
     return PACKET_TYPE_BAD;
@@ -28,10 +33,168 @@ Packet* packet_init(PacketType type, void* data) {
 }
 
 Packet* packet_init_safe(const char* type, const void* data) {
+    if (!data) return NULL;
+
     PacketType t = packet_type_parse(type);
     if (t == PACKET_TYPE_BAD) return NULL;
 
-    if (!data) return NULL;
+    return packet_init(t, (void*)data);
-
+}
-    return packet_init(t, data);
+
+// Per-packet-type encoders.
+static void pack_welcome(
+    yyjson_mut_doc* doc, yyjson_mut_val* data, PacketWelcome* welcome
+) {
+    yyjson_mut_obj_add_uint(doc, data, "id", welcome->id);
+    yyjson_mut_obj_add_int(doc, data, "onlinec", welcome->onlinec);
+    yyjson_mut_val* online = yyjson_mut_arr(doc);
+    for (size_t i = 0; i < welcome->onlinec; i++) {
+        yyjson_mut_val* u = yyjson_mut_obj(doc);
+        yyjson_mut_obj_add_uint(doc, u, "id", welcome->online[i].id);
+        if (welcome->online[i].name)
+            yyjson_mut_obj_add_str(doc, u, "name", *welcome->online[i].name);
+        else yyjson_mut_obj_add_str(doc, u, "name", "");
+        yyjson_mut_arr_add_val(online, u);
+    }
+    yyjson_mut_obj_add_val(doc, data, "online", online);
+
+    yyjson_mut_obj_add_int(doc, data, "historyc", welcome->historyc);
+    yyjson_mut_val* history = yyjson_mut_arr(doc);
+    for (size_t i = 0; i < welcome->historyc; i++) {
+        MsgData* m = welcome->history[i];
+        if (!m) continue;
+        yyjson_mut_val* msg = yyjson_mut_obj(doc);
+        yyjson_mut_obj_add_uint(doc, msg, "id", m->id);
+        yyjson_mut_val* auth = yyjson_mut_obj(doc);
+        yyjson_mut_obj_add_uint(doc, auth, "id", m->author.id);
+        if (m->author.name)
+            yyjson_mut_obj_add_str(doc, auth, "name", *m->author.name);
+        else yyjson_mut_obj_add_str(doc, auth, "name", "");
+        yyjson_mut_obj_add_val(doc, msg, "author", auth);
+        if (m->parent != UINT64_MAX)
+            yyjson_mut_obj_add_uint(doc, msg, "parent", m->parent);
+        else yyjson_mut_obj_add_null(doc, msg, "parent");
+        yyjson_mut_obj_add_str(doc, msg, "content", m->content);
+        yyjson_mut_obj_add_int(doc, msg, "timestamp", m->timestamp);
+        yyjson_mut_arr_add_val(history, msg);
+    }
+    yyjson_mut_obj_add_val(doc, data, "history", history);
+}
+
+static void
+pack_msg_evt(yyjson_mut_doc* doc, yyjson_mut_val* data, PacketMsgEvt* msgevt) {
+    yyjson_mut_obj_add_uint(doc, data, "id", msgevt->id);
+    yyjson_mut_val* authordata = yyjson_mut_obj(doc);
+    yyjson_mut_obj_add_uint(doc, authordata, "id", msgevt->author.id);
+    yyjson_mut_obj_add_str(doc, authordata, "name", *msgevt->author.name);
+    yyjson_mut_obj_add_val(doc, data, "author", authordata);
+    if (msgevt->parent != UINT64_MAX) {
+        yyjson_mut_obj_add_uint(doc, data, "parent", msgevt->parent);
+    } else {
+        yyjson_mut_obj_add_null(doc, data, "parent");
+    }
+    yyjson_mut_obj_add_str(doc, data, "content", msgevt->content);
+    yyjson_mut_obj_add_int(doc, data, "timestamp", msgevt->timestamp);
+}
+
+static void pack_join_evt(
+    yyjson_mut_doc* doc, yyjson_mut_val* data, PacketJoinEvt* joinevt
+) {
+    yyjson_mut_obj_add_uint(doc, data, "id", joinevt->id);
+    yyjson_mut_obj_add_str(doc, data, "name", *joinevt->name);
+}
+
+static void pack_name_evt(
+    yyjson_mut_doc* doc, yyjson_mut_val* data, PacketNameEvt* nameevt
+) {
+    yyjson_mut_val* user = yyjson_mut_obj(doc);
+    yyjson_mut_obj_add_uint(doc, user, "id", nameevt->user.id);
+    yyjson_mut_obj_add_str(doc, user, "name", nameevt->old_name);
+    yyjson_mut_obj_add_val(doc, data, "user", user);
+    yyjson_mut_obj_add_str(doc, data, "new_name", nameevt->new_name);
+}
+
+static void pack_leave_evt(
+    yyjson_mut_doc* doc, yyjson_mut_val* data, PacketJoinEvt* leave
+) {
+    yyjson_mut_obj_add_uint(doc, data, "id", leave->id);
+    yyjson_mut_obj_add_str(doc, data, "name", *leave->name);
+}
+
+static void
+pack_ping(yyjson_mut_doc* doc, yyjson_mut_val* data, PacketPing* p) {
+    yyjson_mut_obj_add_uint(doc, data, "ts", p->ts);
+}
+
+static void
+pack_msg_ack(yyjson_mut_doc* doc, yyjson_mut_val* data, PacketMsgAck* ack) {
+    yyjson_mut_obj_add_str(doc, data, "status", ack->status);
+    yyjson_mut_obj_add_uint(doc, data, "id", ack->id);
+}
+
+static void
+pack_name_ack(yyjson_mut_doc* doc, yyjson_mut_val* data, PacketNameAck* ack) {
+    yyjson_mut_obj_add_str(doc, data, "status", ack->status);
+    yyjson_mut_obj_add_str(doc, data, "name", ack->name);
+}
+
+char* packet_string(Packet* packet, size_t* sz) {
+    yyjson_mut_doc* doc = yyjson_mut_doc_new(NULL);
+
+    // Create document root.
+    yyjson_mut_val* root = yyjson_mut_obj(doc);
+    yyjson_mut_doc_set_root(doc, root);
+
+    // Add the type field.
+    yyjson_mut_obj_add_str(
+        doc, root, "type", packet_type_strings[packet->type]
+    );
+
+    // Create the "data" field.
+    yyjson_mut_val* data = yyjson_mut_obj(doc);
+
+    switch (packet->type) {
+        case PACKET_TYPE_WELCOME:
+            pack_welcome(doc, data, (PacketWelcome*)packet->data);
+            break;
+        case PACKET_TYPE_MSG_EVT:
+            pack_msg_evt(doc, data, (PacketMsgEvt*)packet->data);
+            break;
+        case PACKET_TYPE_JOIN_EVT:
+            pack_join_evt(doc, data, (PacketJoinEvt*)packet->data);
+            break;
+        case PACKET_TYPE_LEAVE_EVT:
+            pack_leave_evt(doc, data, (PacketJoinEvt*)packet->data);
+            break;
+        case PACKET_TYPE_NAME_EVT:
+            pack_name_evt(doc, data, (PacketNameEvt*)packet->data);
+            break;
+        case PACKET_TYPE_PING:
+            pack_ping(doc, data, (PacketPing*)packet->data);
+            break;
+        case PACKET_TYPE_PONG:
+            pack_ping(doc, data, (PacketPing*)packet->data);
+            break;
+        case PACKET_TYPE_MSG_ACK:
+            pack_msg_ack(doc, data, (PacketMsgAck*)packet->data);
+            break;
+        case PACKET_TYPE_NAME_ACK:
+            pack_name_ack(doc, data, (PacketNameAck*)packet->data);
+            break;
+        default:
+            printf(
+                "Something's gone badly wrong. Trying to get string of "
+                "non-sending packet type %d. \n",
+                packet->type
+            );
+            exit(347);
+    }
+
+    // Add data field to root.
+    yyjson_mut_obj_add_val(doc, root, "data", data);
+
+    char* out = yyjson_mut_write(doc, 0, sz);
+    yyjson_mut_doc_free(doc);
+
+    return out;
 }

server/src/chat.c

@@ -3,7 +3,7 @@
 #include "include/data.h"
 #include "include/session.h"
 
-#include <ctype.h>
+#include <inttypes.h>
 #include <libwebsockets.h>
 #include <stdlib.h>
 #include <string.h>
@@ -11,18 +11,14 @@
 #include <yyjson.h>
 
 MsgData* chat_history[CHAT_HISTORY_SZ] = {NULL};
-size_t chat_history_head = 0;
+size_t chat_history_head = 0;  // Next insertion index.
+size_t chat_history_count = 0; // Number of valid entries.
+static MsgID next_msg_id = 1;
 
 MsgData* chat_history_msg_add(MsgData* msg) {
-    if (chat_history_head < CHAT_HISTORY_SZ - 1) {
+    chat_history[chat_history_head] = msg;
-        chat_history[chat_history_head] = msg;
+    chat_history_head = (chat_history_head + 1) % CHAT_HISTORY_SZ;
-        chat_history_head++;
+    if (chat_history_count < CHAT_HISTORY_SZ) { chat_history_count++; }
-    } else if (chat_history_head == CHAT_HISTORY_SZ - 1) {
-        chat_history[chat_history_head] = msg;
-        chat_history_head = 0;
-    } else {
-        exit(132); // Bad.
-    }
 
     return msg;
 }
@@ -30,13 +26,13 @@ MsgData* chat_history_msg_add(MsgData* msg) {
 MsgData** chat_history_nice(void) {
     MsgData** msgs = calloc(CHAT_HISTORY_SZ, sizeof(MsgData*));
 
-    size_t i = chat_history_head, j = 0;
+    // Oldest entry is head - count (mod size).
-    while (true) {
+    size_t start = (chat_history_head + CHAT_HISTORY_SZ - chat_history_count) %
-        if (!chat_history[i]) break;
+                   CHAT_HISTORY_SZ;
-        msgs[j] = chat_history[i];
+
-        i = (i + 1) % CHAT_HISTORY_SZ;
+    for (size_t j = 0; j < chat_history_count; j++) {
-        j++;
+        size_t idx = (start + j) % CHAT_HISTORY_SZ;
-        if (chat_history_head == i) break;
+        msgs[j] = chat_history[idx];
     }
 
     return msgs;
@@ -62,6 +58,7 @@ Packet* packet_parse(const char* in, size_t len) {
 void do_join(Session* sess, Packet* packet) {
     yyjson_val* data = packet->data;
     yyjson_val* jname = data ? yyjson_obj_get(data, "name") : NULL;
+    if (!jname) { jname = data ? yyjson_obj_get(data, "username") : NULL; }
     const char* rname =
         (jname && yyjson_is_str(jname)) ? yyjson_get_str(jname) : "Anon";
 
@@ -72,8 +69,166 @@ void do_join(Session* sess, Packet* packet) {
     session_set_name(sess, name);
 }
 
-// Do a msg packet.
+// Do a welcome packet.
-void do_msg(Session* sess, Packet* packet) {}
+void do_welcome(Session* sess) {
+    // Build list of online users (only sessions with a name).
+    size_t onlinec = 0;
+    for (Session* it = session_get_head(); it; it = it->next)
+        if (session_has_name(it)) onlinec++;
+
+    UserData* online = calloc(onlinec, sizeof(UserData));
+    size_t oi = 0;
+    for (Session* it = session_get_head(); it; it = it->next) {
+        if (!session_has_name(it)) continue;
+        online[oi].id = session_get_id(it);
+        online[oi].name = session_get_name(it);
+        oi++;
+    }
+
+    // Build history list.
+    MsgData** history = chat_history_nice();
+    size_t historyc = 0;
+    while (historyc < CHAT_HISTORY_SZ && history[historyc]) historyc++;
+
+    PacketWelcome data = {
+        .id = session_get_id(sess),
+        .onlinec = onlinec,
+        .online = online,
+        .historyc = historyc,
+        .history = history
+    };
+
+    Packet* packet = packet_init(PACKET_TYPE_WELCOME, &data);
+
+    session_send(sess, packet);
+    free(packet);
+    free(online);
+    free(history);
+}
+
+// Do a welcome packet.
+void do_joinevt(Session* sess) {
+    PacketJoinEvt data = {
+        .id = session_get_id(sess), .name = session_get_name(sess)
+    };
+
+    Packet* packet = packet_init(PACKET_TYPE_JOIN_EVT, &data);
+    session_send_all(packet);
+}
+
+// Do a name change event: user contains OLD name, new_name is the updated name.
+void do_nameevt(Session* sess, const Name old_name, const Name new_name) {
+    PacketNameEvt data = {.user = {.id = session_get_id(sess), .name = NULL}};
+
+    strncpy(data.old_name, old_name, NAME_MAX_LENGTH - 1);
+    data.old_name[NAME_MAX_LENGTH - 1] = '\0';
+    data.user.name = &data.old_name;
+
+    strncpy(data.new_name, new_name, NAME_MAX_LENGTH - 1);
+    data.new_name[NAME_MAX_LENGTH - 1] = '\0';
+
+    Packet* packet = packet_init(PACKET_TYPE_NAME_EVT, &data);
+    session_send_all(packet);
+}
+
+// Handle an incoming client message, store it, and broadcast an event.
+void do_msg(Session* sess, Packet* packet) {
+    if (!sess || !packet) return;
+
+    PacketMsgAck ack = {.id = 0, .status = "success"};
+
+    // Require the sender to have a name.
+    if (!session_has_name(sess)) {
+        ack.status = "unnamed_session";
+        Packet* p = packet_init(PACKET_TYPE_MSG_ACK, &ack);
+        session_send(sess, p);
+        free(p);
+        return;
+    }
+
+    yyjson_val* data = (yyjson_val*)packet->data;
+    if (!data || !yyjson_is_obj(data)) {
+        ack.status = "bad_data";
+        Packet* p = packet_init(PACKET_TYPE_MSG_ACK, &ack);
+        session_send(sess, p);
+        free(p);
+        return;
+    }
+
+    yyjson_val* jcontent = yyjson_obj_get(data, "content");
+    if (!(jcontent && yyjson_is_str(jcontent))) {
+        ack.status = "bad_content";
+        Packet* p = packet_init(PACKET_TYPE_MSG_ACK, &ack);
+        session_send(sess, p);
+        free(p);
+        return;
+    }
+    const char* content = yyjson_get_str(jcontent);
+    if (!msg_verify(content)) {
+        ack.status = "invalid_content";
+        Packet* p = packet_init(PACKET_TYPE_MSG_ACK, &ack);
+        session_send(sess, p);
+        free(p);
+        return;
+    }
+
+    yyjson_val* jparent = yyjson_obj_get(data, "parent");
+    MsgID parent = UINT64_MAX;
+    if (jparent) {
+        if (yyjson_is_int(jparent)) {
+            int64_t v = yyjson_get_int(jparent);
+            if (v >= 0) parent = (MsgID)v;
+        } else if (yyjson_is_str(jparent)) {
+            const char* ps = yyjson_get_str(jparent);
+            if (ps) {
+                char* endp = NULL;
+                unsigned long long tmp = strtoull(ps, &endp, 10);
+                if (endp && *endp == '\0') parent = (MsgID)tmp;
+            }
+        }
+    }
+
+    MsgData* msg = malloc(sizeof(MsgData));
+    if (!msg) {
+        lwsl_err("Failed to allocate MsgData.\n");
+        return;
+    }
+
+    msg->id = next_msg_id++;
+    msg->author.id = session_get_id(sess);
+    msg->author.name = session_get_name(sess);
+    msg->parent = parent;
+    strncpy(msg->content, content, MSG_MAX_LENGTH - 1);
+    msg->content[MSG_MAX_LENGTH - 1] = '\0';
+    msg->timestamp = time(NULL);
+
+    lwsl_notice(
+        "msg from %" PRIu64 " (%s): \"%s\" parent=%s\n", msg->author.id,
+        *msg->author.name, msg->content,
+        (msg->parent == UINT64_MAX ? "null" : "")
+    );
+
+    chat_history_msg_add(msg);
+
+    ack.id = msg->id;
+    Packet* ackp = packet_init(PACKET_TYPE_MSG_ACK, &ack);
+    session_send(sess, ackp);
+    free(ackp);
+
+    Packet* evt = packet_init(PACKET_TYPE_MSG_EVT, msg);
+    session_send_all(evt);
+    free(evt);
+}
+
+static void do_ping(Session* sess) {
+    PacketPing data = {.ts = (uint64_t)time(NULL)};
+    Packet* packet = packet_init(PACKET_TYPE_PING, &data);
+    session_send(sess, packet);
+    free(packet);
+
+    sess->awaiting_pong = true;
+    sess->last_ping_ts = data.ts;
+}
 
 #define CHAT_PACKET_SIZE SESSION_CHAT_BUF_SIZE
 
@@ -88,12 +243,12 @@ int cb_chat(
 ) {
     Session** ps_p = (Session**)user;
     Session* sess = ps_p ? *ps_p : NULL;
-    Session* head = session_get_head();
 
     switch (reason) {
         case LWS_CALLBACK_ESTABLISHED:
             // New connection, create session.
             if (ps_p) { *ps_p = session_create(wsi); }
+            lws_set_timer_usecs(wsi, 10 * LWS_USEC_PER_SEC);
             break;
         case LWS_CALLBACK_RECEIVE: {
             // Parse inc JSON packet.
@@ -107,60 +262,21 @@ int cb_chat(
             Packet* packet = packet_parse(in, len);
 
             if (!packet) {
-                lwsl_warn("Received bad packet: \"%s\".\n", (char*)in);
+                int loglen = (len > 256) ? 256 : (int)len;
+                lwsl_warn(
+                    "Received bad packet: \"%.*s\".\n", loglen, (const char*)in
+                );
                 break;
             }
 
             switch (packet->type) {
                 case PACKET_TYPE_JOIN:
                     // #1. Handle join packet, add new session.
+                    do_welcome(sess);
                     do_join(sess, packet);
-                    //
+                    do_joinevt(sess);
-                    // #2. Welcome the new client.
-                    {
-                        yyjson_mut_doc* wdoc = yyjson_mut_doc_new(NULL);
-                        yyjson_mut_val* wroot = yyjson_mut_obj(wdoc);
-                        yyjson_mut_doc_set_root(wdoc, wroot);
-                        yyjson_mut_obj_add_str(wdoc, wroot, "type", "welcome");
-
-                        yyjson_mut_val* wdata = yyjson_mut_obj(wdoc);
-                        yyjson_mut_obj_add_val(wdoc, wroot, "data", wdata);
-                        yyjson_mut_obj_add_uint(
-                            wdoc, wdata, "you", session_get_id(sess)
-                        );
-
-                        yyjson_mut_val* wusers = yyjson_mut_arr(wdoc);
-                        yyjson_mut_obj_add_val(wdoc, wdata, "users", wusers);
-
-                        for (Session* s = head; s; s = s->next) {
-                            if (session_has_name(s)) {
-                                yyjson_mut_val* uobj = yyjson_mut_obj(wdoc);
-                                /* add each user once */
-                                yyjson_mut_arr_add_val(wusers, uobj);
-                                yyjson_mut_obj_add_uint(
-                                    wdoc, uobj, "id", session_get_id(s)
-                                );
-                                yyjson_mut_obj_add_str(
-                                    wdoc, uobj, "username", session_get_name(s)
-                                );
-                            }
-                        }
-                        // History will be streamed individually after welcome.
-
-                        size_t out_len;
-                        char* out = yyjson_mut_write(wdoc, 0, &out_len);
-                        size_t copy_len = out_len < SESSION_CHAT_BUF_SIZE
-                                              ? out_len
-                                              : SESSION_CHAT_BUF_SIZE;
-                        sess->buf_len = copy_len;
-                        memcpy(&sess->buf[LWS_PRE], out, copy_len);
-                        // Schedule the welcome frame for writable callback.
-                        lws_callback_on_writable(sess->wsi);
-
-                        free(out);
-                        yyjson_mut_doc_free(wdoc);
-                    }
 
+#if 0
                     // #2. Introduce our new client to everybody else.
                     {
                         yyjson_mut_doc* jdoc = yyjson_mut_doc_new(NULL);
@@ -176,7 +292,7 @@ int cb_chat(
                             jdoc, jdata, "id", session_get_id(sess)
                         );
                         yyjson_mut_obj_add_str(
-                            jdoc, jdata, "username", session_get_name(sess)
+                            jdoc, jdata, "username", *session_get_name(sess)
                         );
 
                         size_t out_len;
@@ -185,208 +301,138 @@ int cb_chat(
                                               ? out_len
                                               : SESSION_CHAT_BUF_SIZE;
                         for (Session* s = head; s; s = s->next) {
-                            s->buf_len = copy_len;
+                            session_send_raw(s, out, copy_len);
-                            memcpy(&s->buf[LWS_PRE], out, copy_len);
-                            lws_callback_on_writable(s->wsi);
                         }
                         free(out);
                         yyjson_mut_doc_free(jdoc);
                     }
+#endif
+                    break;
+                case PACKET_TYPE_MSG:  do_msg(sess, packet); break;
+                case PACKET_TYPE_NAME: {
+                    // Extract requested new name.
+                    yyjson_val* pdata = packet->data;
+                    yyjson_val* jname =
+                        pdata ? yyjson_obj_get(pdata, "name") : NULL;
+                    if (!jname) {
+                        jname =
+                            pdata ? yyjson_obj_get(pdata, "username") : NULL;
+                    }
+                    if (!(jname && yyjson_is_str(jname))) {
+                        PacketNameAck ack = {.status = "bad_name"};
+                        Packet* ackp = packet_init(PACKET_TYPE_NAME_ACK, &ack);
+                        session_send(sess, ackp);
+                        free(ackp);
+                        break;
+                    }
+                    const char* rname = yyjson_get_str(jname);
+
+                    Name new_name = {'\0'};
+                    for (size_t i = 0; rname[i] && i < NAME_MAX_LENGTH - 1; i++)
+                        new_name[i] = rname[i];
+
+                    // Capture old name, broadcast event, then update session.
+                    Name old_name = {'\0'};
+                    strncpy(
+                        old_name, *session_get_name(sess), NAME_MAX_LENGTH - 1
+                    );
+                    old_name[NAME_MAX_LENGTH - 1] = '\0';
+
+                    do_nameevt(sess, old_name, new_name);
+                    session_set_name(sess, new_name);
+
+                    PacketNameAck ack = {.status = "success"};
+                    strncpy(ack.name, new_name, NAME_MAX_LENGTH);
+                    ack.name[NAME_MAX_LENGTH - 1] = '\0';
+                    Packet* ackp = packet_init(PACKET_TYPE_NAME_ACK, &ack);
+                    session_send(sess, ackp);
+                    free(ackp);
+                    break;
+                }
+                case PACKET_TYPE_PONG:
+                    // Client responded; nothing else to do (timer continues).
+                    if (sess) {
+                        sess->awaiting_pong = false;
+                        sess->missed_pings = 0;
+                    }
                     break;
-                case PACKET_TYPE_MSG: do_msg(sess, packet); break;
                 default:
                     lwsl_warn(
                         "Received client-only packet: \"%s\".\n", (char*)in
                     );
             }
-        }
+        } break;
-#if 0
+
-        // NAME.
+        case LWS_CALLBACK_TIMER:
-            else if (type && strcmp(type, "name") == 0 && sess &&
+            if (sess) {
-                     session_has_username(sess)) {
+                if (sess->awaiting_pong) {
-                const yyjson_val* dataVal =
+                    sess->missed_pings++;
-                    root ? yyjson_obj_get((yyjson_val*)root, "data") : NULL;
+                    if (sess->missed_pings >= 3) {
-                const yyjson_val* nval =
+                        lwsl_notice(
-                    dataVal ? yyjson_obj_get((yyjson_val*)dataVal, "username")
+                            "Closing session %" PRIu64
-                            : NULL;
+                            " after %u missed pings\n",
-                // Enforce max name length.
+                            session_get_id(sess), sess->missed_pings
-                const char* raw_newname =
+                        );
-                    (nval && yyjson_is_str((yyjson_val*)nval))
+                        lws_close_reason(
-                        ? yyjson_get_str((yyjson_val*)nval)
+                            wsi, LWS_CLOSE_STATUS_GOINGAWAY,
-                        : NULL;
+                            (unsigned char*)"ping timeout", 12
-                char newname_buf[SESSION_USERNAME_MAX_LEN];
+                        );
-                if (raw_newname && raw_newname[0] != '\0') {
+                        return -1;
-                    size_t _j;
-                    for (_j = 0;
-                         raw_newname[_j] && _j < SESSION_USERNAME_MAX_LEN - 1;
-                         ++_j) {
-                        unsigned char c = (unsigned char)raw_newname[_j];
-                        newname_buf[_j] = isprint(c) ? c : '?';
                     }
-                    newname_buf[_j] = '\0';
                 } else {
-                    // Disallow empty names.
+                    sess->missed_pings = 0;
-                    strcpy(newname_buf, session_get_name(sess));
-                }
-                const char* newname = newname_buf;
-                // Buffer old name before updating.
-                char oldname_buf[SESSION_USERNAME_MAX_LEN];
-                const char* current = session_get_name(sess);
-                if (current) {
-                    strncpy(oldname_buf, current, SESSION_USERNAME_MAX_LEN - 1);
-                    oldname_buf[SESSION_USERNAME_MAX_LEN - 1] = '\0';
-                } else {
-                    oldname_buf[0] = '\0';
-                }
-                // Now update to new name.
-                session_set_name(sess, newname);
-
-                // Broadcast name-event to other clients.
-                {
-                    yyjson_mut_doc* ndoc = yyjson_mut_doc_new(NULL);
-                    yyjson_mut_val* nroot = yyjson_mut_obj(ndoc);
-                    yyjson_mut_doc_set_root(ndoc, nroot);
-                    yyjson_mut_obj_add_str(ndoc, nroot, "type", "name-event");
-                    yyjson_mut_val* ndata = yyjson_mut_obj(ndoc);
-                    yyjson_mut_obj_add_val(ndoc, nroot, "data", ndata);
-                    yyjson_mut_obj_add_uint(
-                        ndoc, ndata, "id", session_get_id(sess)
-                    );
-                    yyjson_mut_obj_add_str(ndoc, ndata, "old", oldname_buf);
-                    yyjson_mut_obj_add_str(ndoc, ndata, "new", newname);
-
-                    size_t out_len;
-                    char* out = yyjson_mut_write(ndoc, 0, &out_len);
-                    size_t copy_len = out_len < SESSION_CHAT_BUF_SIZE
-                                          ? out_len
-                                          : SESSION_CHAT_BUF_SIZE;
-                    for (Session* s = head; s; s = s->next) {
-                        s->buf_len = copy_len;
-                        memcpy(&s->buf[LWS_PRE], out, copy_len);
-                        lws_callback_on_writable(s->wsi);
-                    }
-                    free(out);
-                    yyjson_mut_doc_free(ndoc);
                 }
+                do_ping(sess);
+                lws_set_timer_usecs(wsi, 10 * LWS_USEC_PER_SEC);
             }
-            // MSG.
-            else if (type && strcmp(type, "msg") == 0 && sess &&
-                     session_has_username(sess)) {
-                const yyjson_val* data =
-                    yyjson_obj_get((yyjson_val*)root, "data");
-                const yyjson_val* cval =
-                    data ? yyjson_obj_get((yyjson_val*)data, "content") : NULL;
-                // Enforce maximum message content length
-                const char* raw_msg = (cval && yyjson_is_str((yyjson_val*)cval))
-                                          ? yyjson_get_str((yyjson_val*)cval)
-                                          : "";
-                char msg_buf[CHAT_BUF_SIZE];
-                strncpy(msg_buf, raw_msg, CHAT_BUF_SIZE - 1);
-                msg_buf[CHAT_BUF_SIZE - 1] = '\0';
-                // Sanitize message to printable characters.
-                for (size_t _k = 0; msg_buf[_k]; ++_k) {
-                    unsigned char c = (unsigned char)msg_buf[_k];
-                    if (!isprint(c)) { msg_buf[_k] = '?'; }
-                }
-                const char* msg = msg_buf;
-
-                // Build msg-event JSON with ID, parent and timestamp.
-                // Get parent ID if present.
-                const yyjson_val* dataVal =
-                    yyjson_obj_get((yyjson_val*)root, "data");
-                const yyjson_val* pval =
-                    dataVal ? yyjson_obj_get((yyjson_val*)dataVal, "parent")
-                            : NULL;
-                uint64_t parent_id = (pval && yyjson_is_uint((yyjson_val*)pval))
-                                         ? yyjson_get_uint((yyjson_val*)pval)
-                                         : 0;
-                time_t now = time(NULL);
-                size_t msg_id = next_msg_id++;
-                // Send ack with the new message ID.
-                {
-                    yyjson_mut_doc* ackdoc = yyjson_mut_doc_new(NULL);
-                    yyjson_mut_val* ackroot = yyjson_mut_obj(ackdoc);
-                    yyjson_mut_doc_set_root(ackdoc, ackroot);
-                    yyjson_mut_obj_add_str(ackdoc, ackroot, "type", "msg-ack");
-                    yyjson_mut_val* ackdat = yyjson_mut_obj(ackdoc);
-                    yyjson_mut_obj_add_val(ackdoc, ackroot, "data", ackdat);
-                    yyjson_mut_obj_add_uint(ackdoc, ackdat, "id", msg_id);
-                    size_t ack_len;
-                    char* ack_out = yyjson_mut_write(ackdoc, 0, &ack_len);
-                    size_t copy_ack = ack_len < SESSION_CHAT_BUF_SIZE
-                                          ? ack_len
-                                          : SESSION_CHAT_BUF_SIZE;
-                    sess->buf_len = copy_ack;
-                    memcpy(&sess->buf[LWS_PRE], ack_out, copy_ack);
-                    lws_write(
-                        sess->wsi, &sess->buf[LWS_PRE], sess->buf_len,
-                        LWS_WRITE_TEXT
-                    );
-
-                    free(ack_out);
-                    yyjson_mut_doc_free(ackdoc);
-                }
-
-                yyjson_mut_doc* mdoc = yyjson_mut_doc_new(NULL);
-                yyjson_mut_val* mroot = yyjson_mut_obj(mdoc);
-                yyjson_mut_doc_set_root(mdoc, mroot);
-                yyjson_mut_obj_add_str(mdoc, mroot, "type", "msg-event");
-
-                yyjson_mut_val* mdat = yyjson_mut_obj(mdoc);
-                yyjson_mut_obj_add_val(mdoc, mroot, "data", mdat);
-                yyjson_mut_obj_add_uint(mdoc, mdat, "id", msg_id);
-                if (parent_id)
-                    yyjson_mut_obj_add_uint(mdoc, mdat, "parent", parent_id);
-                else yyjson_mut_obj_add_null(mdoc, mdat, "parent");
-                yyjson_mut_obj_add_uint(mdoc, mdat, "ts", (uint64_t)now);
-                yyjson_mut_obj_add_str(
-                    mdoc, mdat, "username", session_get_name(sess)
-                );
-                yyjson_mut_obj_add_str(mdoc, mdat, "content", msg);
-
-                size_t out_len;
-                char* out = yyjson_mut_write(mdoc, 0, &out_len);
-                // Store this msg-event JSON in the circular history buffer.
-                if (history_count == HISTORY_SIZE) {
-                    free(history[history_pos]);
-                } else {
-                    history_count++;
-                }
-                history[history_pos] = strdup(out);
-                history_len[history_pos] = out_len;
-                history_pos = (history_pos + 1) % HISTORY_SIZE;
-                size_t copy_len = out_len < SESSION_CHAT_BUF_SIZE
-                                      ? out_len
-                                      : SESSION_CHAT_BUF_SIZE;
-                for (Session* s = head; s; s = s->next) {
-                    s->buf_len = copy_len;
-                    memcpy(&s->buf[LWS_PRE], out, copy_len);
-                    lws_callback_on_writable(s->wsi);
-                }
-                free(out);
-                yyjson_mut_doc_free(mdoc);
-                // Writable events already scheduled for each session above.
-            }
-
-            yyjson_doc_free(doc);
             break;
-    }
-#endif
 
         case LWS_CALLBACK_SERVER_WRITEABLE:
-            if (sess && sess->buf_len > 0) {
+            if (!sess->queue_head) break;
-                lws_write(
+
-                    sess->wsi, &sess->buf[LWS_PRE], sess->buf_len,
+            MsgNode* node = sess->queue_head;
-                    LWS_WRITE_TEXT
+
-                );
+            // Send the data at payload + LWS_PRE.
-                sess->buf_len = 0;
+            lwsl_notice(
-            }
+                "write to session %" PRIu64 " len=%zu queue=%zu\n",
+                session_get_id(sess), node->ln, sess->queue_count
+            );
+            int m = lws_write(
+                wsi, &node->payload[LWS_PRE], node->ln, LWS_WRITE_TEXT
+            );
+            if (m < 0) return -1; // Socket error, kill connection.
+
+            // Pop the queue.
+            sess->queue_head = node->nxt;
+            if (!sess->queue_head) { sess->queue_tail = NULL; }
+            sess->queue_count--;
+
+            free(node);
+
+            // If there are still messages left, notice them.
+            if (sess->queue_head) { lws_callback_on_writable(wsi); }
+
             break;
 
         case LWS_CALLBACK_CLOSED:
             // Goodbye.
-            // TODO: Add leave event to proto.
+            if (sess) {
-            if (sess) { session_destroy(sess); }
+                // Broadcast leave event before destroying.
+                PacketJoinEvt leave = {
+                    .id = session_get_id(sess), .name = session_get_name(sess)
+                };
+                Packet* evt = packet_init(PACKET_TYPE_LEAVE_EVT, &leave);
+                session_send_all(evt);
+                free(evt);
+
+                MsgNode* current = sess->queue_head;
+                while (current) {
+                    MsgNode* tmp = current;
+                    current = current->nxt;
+                    free(tmp);
+                }
+                session_destroy(sess);
+            }
             break;
 
         default: break;

server/src/include/api.h

@@ -4,12 +4,19 @@
 #include "data.h"
 
 typedef enum {
-    PACKET_TYPE_JOIN,     // C -> S.
+    PACKET_TYPE_JOIN,      // C -> S.
-    PACKET_TYPE_WELCOME,  // S -> C.
+    PACKET_TYPE_WELCOME,   // S -> C.
-    PACKET_TYPE_JOIN_EVT, // S->A.
+    PACKET_TYPE_JOIN_EVT,  // S->A.
-    PACKET_TYPE_MSG,      // C->S.
+    PACKET_TYPE_MSG,       // C->S.
-    PACKET_TYPE_MSG_EVT,  // S->A.
+    PACKET_TYPE_MSG_EVT,   // S->A.
-    PACKET_TYPE_MAX = PACKET_TYPE_MSG_EVT,
+    PACKET_TYPE_NAME,      // C->S. Set/update name after connect.
+    PACKET_TYPE_NAME_EVT,  // S->A. Broadcast when a name changes.
+    PACKET_TYPE_PING,      // S -> C. Liveness ping.
+    PACKET_TYPE_PONG,      // C -> S. Liveness pong.
+    PACKET_TYPE_MSG_ACK,   // S -> C. Acknowledge message submission.
+    PACKET_TYPE_NAME_ACK,  // S -> C. Acknowledge name change.
+    PACKET_TYPE_LEAVE_EVT, // S -> A. Broadcast when a user leaves.
+    PACKET_TYPE_MAX = PACKET_TYPE_LEAVE_EVT,
     PACKET_TYPE_BAD,
 } PacketType;
 
@@ -27,6 +34,9 @@ Packet* packet_init(PacketType type, void* data);
 // Create a packet from untrusted data.
 Packet* packet_init_safe(const char* type, const void* data);
 
+// Get a string representation of a packet.
+char* packet_string(Packet* packet, size_t* sz);
+
 typedef struct {
     Name name; // Your selected name.
 } PacketJoin;
@@ -36,12 +46,10 @@ typedef struct {
     size_t onlinec;   // The number of users online.
     UserData* online; // The list of online users.
     size_t historyc;  // The number of messages in history.
-    MsgData* history; // The list of historical messages.
+    MsgData** history; // The list of historical messages.
 } PacketWelcome;
 
-typedef struct {
+typedef UserData PacketJoinEvt;
-    UserData newguy; // Who just joined.
-} PacketJoinEvent;
 
 typedef struct {
     MsgContent content; // The content of the message.
@@ -50,4 +58,26 @@ typedef struct {
 
 typedef MsgData PacketMsgEvt;
 
+typedef struct {
+    UserData user; // The user who changed their name.
+    Name old_name; // The previous name (for serialization via user.name).
+    Name new_name; // The updated name.
+} PacketNameEvt;
+
+typedef struct {
+    uint64_t ts; // Unix timestamp when ping was sent.
+} PacketPing;
+
+typedef PacketPing PacketPong;
+
+typedef struct {
+    MsgID id;          // Assigned message ID (0 on failure).
+    const char* status; // "success" or error reason.
+} PacketMsgAck;
+
+typedef struct {
+    const char* status; // "success" or error reason.
+    Name name;          // The name that was applied (empty on failure).
+} PacketNameAck;
+
 #endif

server/src/include/chat.h

@@ -10,7 +10,8 @@
 // Message history (ring).
 #define CHAT_HISTORY_SZ 128
 extern MsgData* chat_history[CHAT_HISTORY_SZ];
-extern size_t chat_history_head; // Points to the oldest message, or is NULL.
+extern size_t chat_history_head; // Next insertion index.
+extern size_t chat_history_count; // Number of valid history entries.
 
 // Add message to history ring.
 MsgData* chat_history_msg_add(MsgData* msg);

server/src/include/data.h

@@ -2,12 +2,13 @@
 #define DATA__H
 
 #include <time.h>
+#include <stdint.h>
 
 #define NAME_MAX_LENGTH 16
 #define MSG_MAX_LENGTH 1024
 
-typedef int UserID;
+typedef uint64_t UserID;
-typedef int MsgID;
+typedef uint64_t MsgID;
 
 typedef char Name[NAME_MAX_LENGTH];
 int name_verify(const char* name);
@@ -17,7 +18,7 @@ int msg_verify(const char* content);
 
 typedef struct {
     UserID id;
-    Name name;
+    Name* name;
 } UserData;
 
 typedef struct {

server/src/include/session.h

@@ -1,28 +1,40 @@
 #ifndef SESSION__H
 #define SESSION__H
 
+#include "api.h"
+#include "data.h"
+
 #include <libwebsockets.h>
 #include <stdbool.h>
 #include <stdint.h>
 
-#include "data.h"
-
 // Includes terminating null.
 #define SESSION_CHAT_BUF_SIZE 32768
 
+// Linked list of messages in queue to send.
+typedef struct MSG_NODE_STRUCT {
+    struct MSG_NODE_STRUCT* nxt;
+    size_t ln;
+    unsigned char payload[];
+} MsgNode;
+
 /**
- * session_t
+ * Session
  * Represents a single WebSocket client session in the chat server.
  */
 typedef struct SESSION {
     struct lws* wsi;      // Libwebsockets connection handle.
     uint64_t id;          // Unique session ID.
     struct SESSION* next; // Next session in the internal list.
-    Name name;            // Stored name.
+    Name name;           // Stored name.
     bool named;           // True once name is set.
-    unsigned char
+    size_t queue_count;   // Number of pending messages in the queue.
-        buf[LWS_PRE + SESSION_CHAT_BUF_SIZE]; // Outgoing buffer per session
+    MsgNode* queue_head;  // First to send.
-    size_t buf_len;                           // Length of data in buf
+    MsgNode* queue_tail;  // Last.
+    bool awaiting_pong;   // True if a ping is outstanding.
+    unsigned missed_pings; // Consecutive missed pongs.
+    uint64_t last_ping_ts; // Timestamp of last ping sent.
+
 } Session;
 
 /**
@@ -50,6 +62,21 @@ void session_destroy(Session* sess);
  */
 Session* session_get_head(void);
 
+// Handles memory allocation and pointing logic.
+void session_send_raw(Session* sess, const char* data, size_t ln);
+
+/**
+ * session_send
+ * Send a packet to this session.
+ *
+ * @param sess      The session to send to
+ * @param packet    The packet to send.
+ */
+void session_send(Session* sess, Packet* packet);
+
+// Send a packet to all sessions.
+void session_send_all(Packet* packet);
+
 /**
  * session_broadcast
  * Iterate every session in the internal list and invoke the callback.
@@ -75,7 +102,7 @@ void session_set_name(Session* sess, const char* name);
  * @param sess  The session to query.
  * @return      Pointer to the stored name (readonly).
  */
-const char* session_get_name(const Session* sess);
+Name* session_get_name(Session* sess);
 
 /**
  * session_has_name

server/src/session.c

@@ -1,6 +1,8 @@
 #include "include/session.h"
+#include "include/api.h"
 #include "include/data.h"
 
+#include <libwebsockets.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
@@ -18,6 +20,11 @@ Session* session_create(struct lws* wsi) {
     sess->named = false;
     sess->name[0] = '\0';
     sess->next = head;
+    sess->queue_count = 0;
+    sess->queue_head = sess->queue_tail = NULL;
+    sess->awaiting_pong = false;
+    sess->missed_pings = 0;
+    sess->last_ping_ts = 0;
     head = sess;
     return sess;
 }
@@ -37,6 +44,74 @@ void session_destroy(Session* sess) {
 
 Session* session_get_head(void) { return head; }
 
+void session_send_raw(Session* sess, const char* data, size_t ln) {
+    if (!sess || !data) return;
+
+    if (sess->queue_count > 4) {
+        lwsl_warn(
+            "Session %ld queue full, dropping future packets!\n", sess->id
+        );
+    }
+
+    MsgNode* node = malloc(sizeof(MsgNode) + LWS_PRE + ln);
+    if (!node) return;
+
+    node->nxt = NULL;
+    node->ln = ln;
+    // Copy data into payload, leaving LWS_PRE bytes at the start.
+    memcpy(&node->payload[LWS_PRE], data, ln);
+
+    // Append to the tail of the linked list.
+    if (sess->queue_tail) {
+        sess->queue_tail->nxt = node;
+        sess->queue_tail = node;
+    } else {
+        sess->queue_head = sess->queue_tail = node;
+    }
+
+    sess->queue_count++;
+
+    // Tell LWS there's something to write.
+    lwsl_notice(
+        "enqueue to session %" PRIu64 " len=%zu queue=%zu\n", sess->id, ln,
+        sess->queue_count
+    );
+    lws_callback_on_writable(sess->wsi);
+}
+
+void session_send(Session* sess, Packet* packet) {
+    if (!packet) return;
+
+    size_t out_len;
+    char* out = packet_string(packet, &out_len);
+
+    // Check for overflow.
+    if (out_len > SESSION_CHAT_BUF_SIZE) {
+        free(out);
+        return;
+    }
+
+    session_send_raw(sess, out, out_len);
+
+    free(out);
+}
+
+void session_send_all(Packet* packet) {
+    if (!packet) return;
+
+    size_t out_ln;
+    char* out = packet_string(packet, &out_ln);
+    if (!out) return;
+
+    size_t copy_ln =
+        out_ln < SESSION_CHAT_BUF_SIZE ? out_ln : SESSION_CHAT_BUF_SIZE;
+
+    for (Session* s = session_get_head(); s; s = s->next)
+        session_send_raw(s, out, copy_ln);
+
+    free(out);
+}
+
 void session_broadcast(void (*cb)(Session* s, void* user), void* user) {
     for (Session* iter = head; iter; iter = iter->next) { cb(iter, user); }
 }
@@ -48,9 +123,9 @@ void session_set_name(Session* sess, const char* name) {
     sess->named = true;
 }
 
-const char* session_get_name(const Session* sess) {
+Name* session_get_name(Session* sess) {
     if (!sess) { return NULL; }
-    return sess->name;
+    return &sess->name;
 }
 
 bool session_has_name(const Session* sess) {