My backend API services are hosted on AWS using API Gateway and EC2 instance. The backend is built with Node.js/Express JS, and socket.io is used for real-time messaging.
const initializeExpress = (): void => {
const app = express();
let http = require("http").createServer(app);
let io = require("socket.io")(http, {
cors: {}
});
io.on("connection", function(socket: any) {
socket.on("hello", (res) => {
console.log('on hello: ', res);
});
});
const server = http.listen(parseInt(process.env.PORT) || 3001, function() {
console.log("listening on *:3001");
});
// register some middlewares for web socket
...
};
The WebSocket connection works fine in the local environment at 127.0.0.1:3001. However, when moving to the AWS API Gateway configuration, all other API endpoints work except the WebSocket request which returns a 404 error.
error: User undefined got Error on NLB-myapp-internal-1234123.elb.ap-northeast-1.amazonaws.com/socket.io?EIO=4&t=Nv2sCMO&transport=polling: Error: Route '/socket.io?EIO=4&t=Nv2sCMO&transport=polling' does not exist.
Even though the restful API created in AWS API Gateway is configured correctly with proxy integration, the route /socket.io seems to be missing.
I have followed suggestions from related answers but still face the issue. The setup in Express for socket.io is as follows:
const app = express();
let http = require("http").createServer(app);
let io = require("socket.io")(http, {
cors: {}
});
const server = http.listen(parseInt(process.env.PORT) || 3001, function() {
console.log("listening on *:3001");
});
In the local dev environment without API Gateway, everything works smoothly once the request reaches the target port. Why, in the AWS API Gateway setup, does it complain about the non-existent /socket.io route even after successfully delivering the request to the target port?
What am I missing here?