Socket.IO server for Deno

An implementation of the Socket.IO protocol for Deno.

Table of content:

Usage

import { serve } from "https://deno.land/std@0.150.0/http/server.ts";
import { Server } from "https://deno.land/x/socket_io@0.2.0/mod.ts";

const io = new Server();

io.on("connection", (socket) => {
  console.log(`socket ${socket.id} connected`);

  socket.emit("hello", "world");

  socket.on("disconnect", (reason) => {
    console.log(`socket ${socket.id} disconnected due to ${reason}`);
  });
});

await serve(io.handler(), {
  port: 3000,
});

And then run with:

$ deno run --allow-net index.ts

Like the Node.js server, you can also provide types for the events sent between the server and the clients:

interface ServerToClientEvents {
  noArg: () => void;
  basicEmit: (a: number, b: string, c: Buffer) => void;
  withAck: (d: string, callback: (e: number) => void) => void;
}

interface ClientToServerEvents {
  hello: () => void;
}

interface InterServerEvents {
  ping: () => void;
}

interface SocketData {
  user_id: string;
}

const io = new Server<
  ClientToServerEvents,
  ServerToClientEvents,
  InterServerEvents,
  SocketData
>();

Options

path

Default value: /socket.io/

It is the name of the path that is captured on the server side.

Caution! The server and the client values must match (unless you are using a path-rewriting proxy in between).

Example:

const io = new Server(httpServer, {
  path: "/my-custom-path/",
});

connectTimeout

Default value: 45000

The number of ms before disconnecting a client that has not successfully joined a namespace.

pingTimeout

Default value: 20000

This value is used in the heartbeat mechanism, which periodically checks if the connection is still alive between the server and the client.

The server sends a ping, and if the client does not answer with a pong within pingTimeout ms, the server considers that the connection is closed.

Similarly, if the client does not receive a ping from the server within pingInterval + pingTimeout ms, the client also considers that the connection is closed.

pingInterval

Default value: 25000

See pingTimeout for more explanation.

upgradeTimeout

Default value: 10000

This is the delay in milliseconds before an uncompleted transport upgrade is cancelled.

maxHttpBufferSize

Default value: 1e6 (1 MB)

This defines how many bytes a single message can be, before closing the socket. You may increase or decrease this value depending on your needs.

allowRequest

Default value: -

A function that receives a given handshake or upgrade request as its first parameter, and can decide whether to continue or not.

Example:

const io = new Server({
  allowRequest: (req, connInfo) => {
    return Promise.reject("thou shall not pass");
  },
});

cors

Default value: -

A set of options related to Cross-Origin Resource Sharing (CORS).

Example:

const io = new Server({
  cors: {
    origin: ["https://example.com"],
    allowedHeaders: ["my-header"],
    credentials: true,
  },
});

editHandshakeHeaders

Default value: -

A function that allows to edit the response headers of the handshake request.

Example:

const io = new Server({
  editHandshakeHeaders: (responseHeaders, req, connInfo) => {
    responseHeaders.set("set-cookie", "sid=1234");
  },
});

editResponseHeaders

Default value: -

A function that allows to edit the response headers of all requests.

Example:

const io = new Server({
  editResponseHeaders: (responseHeaders, req, connInfo) => {
    responseHeaders.set("my-header", "abcd");
  },
});

Logs

The library relies on the standard log module, so you can display the internal logs of the Socket.IO server with:

import * as log from "https://deno.land/std@0.150.0/log/mod.ts";

await log.setup({
  handlers: {
    console: new log.handlers.ConsoleHandler("DEBUG"),
  },
  loggers: {
    "socket.io": {
      level: "DEBUG",
      handlers: ["console"],
    },
    "engine.io": {
      level: "DEBUG",
      handlers: ["console"],
    },
  },
});

Adapters

Custom adapters can be used to broadcast packets between several Socket.IO servers.

Redis adapter

Documentation: https://socket.io/docs/v4/redis-adapter/

import { serve } from "https://deno.land/std/http/server.ts";
import {
  createRedisAdapter,
  createRedisClient,
  Server,
} from "https://deno.land/x/socket_io/mod.ts";

const [pubClient, subClient] = await Promise.all([
  createRedisClient({
    hostname: "localhost",
  }),
  createRedisClient({
    hostname: "localhost",
  }),
]);

const io = new Server({
  adapter: createRedisAdapter(pubClient, subClient),
});

await serve(io.handler(), {
  port: 3000,
});

License

ISC