diff --git a/ServerMessage.ts b/ServerMessage.ts
index 1b9ef1b..67e74e3 100644
--- a/ServerMessage.ts
+++ b/ServerMessage.ts
@@ -4,6 +4,7 @@ export enum MessageType {
   ID_RESPONSE = 3,
   TYPING = 4,
   CURRENTLY_TYPING = 5,
+  CONNECTED_USERS = 6,
 }
 
 export type ServerMessage = {
@@ -110,15 +111,67 @@ export function isCurrentlyTypingMessage(
   if (
     !Object.hasOwnProperty.call(obj, "currently") ||
     typeof obj !== "object" ||
-    !(
-      (obj as ServerMessage & { currently: unknown }).currently instanceof Array
-    ) ||
-    Array.prototype.some.call(
+    !Array.isArray((obj as ServerMessage & { currently: unknown }).currently) ||
+    !Array.prototype.every.call(
       (obj as ServerMessage & { currently: unknown[] }).currently,
-      (element) => typeof element !== "string"
+      (element) => typeof element === "string"
     )
   ) {
     return false;
   }
   return true;
 }
+
+export type ConnectedUser = {
+  id: string;
+  desiredName?: string;
+};
+export function isConnectedUser(obj: unknown): obj is ConnectedUser {
+  if (typeof obj !== "object" || obj === null) {
+    return false;
+  }
+  if (
+    !Object.prototype.hasOwnProperty.call(obj, "id") ||
+    typeof (obj as { id: unknown }).id !== "string"
+  ) {
+    return false;
+  }
+  if (
+    Object.prototype.hasOwnProperty.call(obj, "desiredName") &&
+    typeof (obj as { desiredName: unknown }).desiredName !== "string"
+  ) {
+    return false;
+  }
+  return true;
+}
+
+export type ConnectedUsersMessage = ServerMessage & {
+  type: MessageType.CONNECTED_USERS;
+  connected: ConnectedUser[];
+};
+export function isConnectedUsersMessage(
+  obj: unknown
+): obj is ConnectedUsersMessage {
+  if (!isServerMessage(obj, MessageType.CONNECTED_USERS)) {
+    return false;
+  }
+
+  if (
+    typeof (obj as ServerMessage & { connected: unknown }).connected !==
+      "object" ||
+    !Array.isArray((obj as ServerMessage & { connected: unknown }).connected)
+  ) {
+    return false;
+  }
+
+  if (
+    !Array.prototype.every.call(
+      (obj as ServerMessage & { connected: unknown[] }).connected,
+      (maybeUser) => isConnectedUser(maybeUser)
+    )
+  ) {
+    return false;
+  }
+
+  return false;
+}