Remove CH-sending timer

CH is an application-level keepalive packet that clients periodically
send for two reasons:

1. It tells the server they're still connected, preventing timeouts.

2. By measuring latency between sending CH and receiving CHECK, a client
   can display ping.

Keepalive is redundant because WebSocket can handle that via PING frames on a
transport layer. WebAO also completely ignores CHECK and sends CH every
five seconds, which is superfluous (AO2 Client sends it once every 45
seconds, in comparison).

Sending CH via `setInterval` was also problematic: browsers seem to
throttle it when the tab becomes inactive, preventing periodic pings and
leading to the server disconnecting inactive browser clients.

3 files changed, 1 insertions, 21 deletions

diff --git a/webAO/client.ts b/webAO/client.ts
index ca53173f..94caf0cb 100644
--- a/webAO/client.ts
+++ b/webAO/client.ts
@@ -143,7 +143,6 @@ class Client extends EventEmitter {
   selectedEmote: number;
   selectedEvidence: number;
   sender: ISender;
-  checkUpdater: any;
   _lastTimeICReceived: any;
   viewport: Viewport;
   partial_packet: boolean;
@@ -207,7 +206,6 @@ class Client extends EventEmitter {
     this.resources = getResources(AO_HOST, theme);
     this.selectedEmote = -1;
     this.selectedEvidence = -1;
-    this.checkUpdater = null;
     this.sender = sender;
     this.viewport = masterViewport();
     this._lastTimeICReceived = new Date(0);
@@ -266,9 +264,6 @@ class Client extends EventEmitter {
       document.getElementById("client_charselect").remove();
       document.getElementById("client_ooc").remove();
     }
-    if (mode !== "replay") {
-      this.checkUpdater = setInterval(() => this.sender.sendCheck(), 5000);
-    }
   }
 
   /**
@@ -384,12 +379,8 @@ class Client extends EventEmitter {
     this.cleanup();
   }
 
-  /**
-   * Stop sending keepalives to the server.
-   */
   cleanup() {
-    clearInterval(this.checkUpdater);
-    if (this.serv) this.serv.close();
+    this.serv.close();
   }
 
   /**
diff --git a/webAO/client/sender/index.ts b/webAO/client/sender/index.ts
index e218b6bc..b9e2b4f4 100644
--- a/webAO/client/sender/index.ts
+++ b/webAO/client/sender/index.ts
@@ -1,7 +1,6 @@
 import { sendIC } from "./sendIC";
 import { sendSelf } from "./sendSelf";
 import { sendServer } from "./sendServer";
-import { sendCheck } from "./sendCheck";
 import { sendHP } from "./sendHP";
 import { sendOOC } from "./sendOOC";
 import { sendCharacter } from "./sendCharacter";
@@ -43,7 +42,6 @@ export interface ISender {
   ) => void;
   sendSelf: (message: string) => void;
   sendServer: (message: string) => void;
-  sendCheck: () => void;
   sendHP: (side: number, hp: number) => void;
   sendOOC: (message: string) => void;
   sendCharacter: (character: number) => void;
@@ -59,7 +57,6 @@ export const sender = {
   sendIC,
   sendSelf,
   sendServer,
-  sendCheck,
   sendHP,
   sendOOC,
   sendCharacter,
diff --git a/webAO/client/sender/sendCheck.ts b/webAO/client/sender/sendCheck.ts
deleted file mode 100644
index 7eb47510..00000000
--- a/webAO/client/sender/sendCheck.ts
+++ /dev/null
@@ -1,8 +0,0 @@
-import { client } from "../../client";
-
-/**
- * Sends a keepalive packet.
- */
-export const sendCheck = () => {
-  client.sender.sendServer(`CH#${client.charID}#%`);
-};