Use APP_PORT consistently

server.js

@@ -3,7 +3,7 @@ const fs = require("fs");
 const http = require("http");
 const path = require("path");
 
-const port = Number(process.env.PORT || 3000);
+const appPort = Number(process.env.APP_PORT || 8787);
 const root = __dirname;
 const clients = new Map();
 const rooms = new Map();
@@ -286,6 +286,6 @@ function encodeFrame(message) {
   return Buffer.concat([header, payload]);
 }
 
-server.listen(port, () => {
-  console.log(`Tictactics multiplayer server running at http://localhost:${port}`);
+server.listen(appPort, () => {
+  console.log(`Tictactics multiplayer server running at http://localhost:${appPort}`);
 });