add ping pong

src/rtmt/rtmt_websocket.ts

@@ -1,11 +1,16 @@
 import { decode, encode } from "./encode_decode_message";
 import { Bytes, OnMessage, RTMT } from "./rtmt";
 import { server } from "../service/http_service";
+import { channel_ping, channel_pong } from "../const/channel_names";
+
+const PING_INTERVAL = 3000, PING_INTERVAL_BUFFER_TIME = 500;
 
 export class RTMTWS implements RTMT {
   private messageChannels: Map<String, OnMessage>;
   private ws: WebSocket;
 
+  private pingTimeout?: number = undefined;
+
   constructor() {
     this.messageChannels = new Map<String, OnMessage>();
   }
@@ -22,11 +27,13 @@ export class RTMTWS implements RTMT {
     ws.onopen = () => {
       console.info("(RTMT) ws has opened");
       this.ws = ws;
+      this.heartbeat();
       onopen();
     };
     ws.onclose = () => {
       console.info("(RTMT) ws has closed");
       //this.ws = undefined
+      clearTimeout(this.pingTimeout);
       onClose();
     };
 
@@ -40,6 +47,20 @@ export class RTMTWS implements RTMT {
     });
   }
 
+  heartbeat() {
+    clearTimeout(this.pingTimeout);
+
+    // Use `WebSocket#terminate()`, which immediately destroys the connection,
+    // instead of `WebSocket#close()`, which waits for the close timer.
+    // Delay should be equal to the interval at which your server
+    // sends out pings plus a conservative assumption of the latency.
+    this.pingTimeout = setTimeout(() => {
+      this.ws.close();
+      this.ws.onclose?.(new CloseEvent("CONNECTION_LOST"));
+    }, PING_INTERVAL + PING_INTERVAL_BUFFER_TIME);
+  }
+
+
   sendMessage(channel: string, message: Object) {
     if (this.ws === undefined) {
       console.error("(RTMT) ws is undefined");
@@ -59,6 +80,11 @@ export class RTMTWS implements RTMT {
   }
 
   onMessage(channel: string, message: Bytes) {
+    if(channel === channel_ping) {
+      this.heartbeat();
+      this.sendMessage(channel_pong, {});
+      return;
+    }
     const callback = this.messageChannels.get(channel);
 
     if (callback) {