Some things.

public/main.js

@@ -12,7 +12,14 @@ ws.onmessage = (event) => {
 function sendMessage() {
   const text = input.value;
   if (text.trim()) {
-    ws.send(text);
+    ws.send(
+      JSON.stringify({
+        type: "send",
+        data: {
+          content: text,
+        },
+      }),
+    );
     input.value = "";
   }
 }