add connection checking

src/Protocol.ts

@@ -7,4 +7,5 @@ export interface ProtocolMessage {
 export enum ProtocolOperation {
     UploadFile = 0,
     ACK = 1,
+    NOP = 2,
 }

src/VM.ts

@@ -12,6 +12,9 @@ export default class VM {
     #socket : Socket;
     #writeLock : Mutex = new Mutex();
     #fileQueue : Queue<File> = new Queue<File>();
+    #nopTimeout : NodeJS.Timeout | null = null;
+    isConnectedToVM : boolean = false;
+    #noNop : boolean = false;
     connected : boolean = false;
     #events : EventEmitter;
     constructor(socketpath : string) {
@@ -88,12 +91,31 @@ export default class VM {
             return;
         }
         var msg = msgpack.decode(payload) as protocol.ProtocolMessage;
+        if (!this.isConnectedToVM) {
+            if (this.#fileQueue.size > 0) this.fileQueueLoop();
+            this.isConnectedToVM = true;
+            this.#noNop = false;
+            this.#nopTimeout = setInterval(() => this.#nopTimeoutFunc(), 5000);
+        }
         switch (msg.Operation) {
             case protocol.ProtocolOperation.ACK:
                 this.#events.emit('ack');
                 break;
         }
     }
+
+    #nopTimeoutFunc() {
+        if (!this.#noNop) {
+            var payload : protocol.ProtocolMessage = {
+                Operation: protocol.ProtocolOperation.NOP
+            };
+            var data = msgpack.encode(payload);
+            this.#sendMessage(data);
+            this.#noNop = true;
+        } else {
+            this.isConnectedToVM = false;
+        }
+    }
 }
 
 function sleep(ms : number) : Promise<void> {