Add RealtimeChannel.sendState and mark STATE messages as those that…

… require an ACK

src/common/lib/client/realtimechannel.ts

@@ -511,6 +511,17 @@ class RealtimeChannel extends EventEmitter {
     this.sendMessage(msg, callback);
   }
 
+  sendState(state: StateMessage[]): Promise<void> {
+    return new Promise((resolve, reject) => {
+      const msg = protocolMessageFromValues({
+        action: actions.STATE,
+        channel: this.name,
+        state,
+      });
+      this.sendMessage(msg, (err) => (err ? reject(err) : resolve()));
+    });
+  }
+
   // Access to this method is synchronised by ConnectionManager#processChannelMessage, in order to synchronise access to the state stored in _decodingContext.
   async processMessage(message: ProtocolMessage): Promise<void> {
     if (

src/common/lib/transport/protocol.ts

@@ -20,7 +20,8 @@ export class PendingMessage {
     this.merged = false;
     const action = message.action;
     this.sendAttempted = false;
-    this.ackRequired = action == actions.MESSAGE || action == actions.PRESENCE;
+    this.ackRequired =
+      typeof action === 'number' && [actions.MESSAGE, actions.PRESENCE, actions.STATE].includes(action);
   }
 }