> For the complete documentation index, see [llms.txt](https://www.socketio4j.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.socketio4j.org/home.md).
# Socketio4j Documentation
Welcome to your team’s developer platform
The Socketio4j Project
Socket.IO server implemented on Java. Realtime java framework
### Get started in 5 minutes
Your first server should be the easiest step. With well-defined endpoints and copy-paste-ready examples, setup is fast and predictable.\
From zero to a working connection in minutes.
Get started API reference
### Server
{% tabs %}
{% tab title="Core Java" %}
{% code title="Server.java" overflow="wrap" expandable="true" %}
```java
//package com.socketio4j.examples.core;
import com.socketio4j.socketio.Configuration;
import com.socketio4j.socketio.SocketIOServer;
import com.socketio4j.socketio.SocketIOClient;
public final class BasicServer {
public static void main(String[] args) {
Configuration config = new Configuration();
config.setHostname("0.0.0.0");
config.setPort(9092);
SocketIOServer server = new SocketIOServer(config);
server.addConnectListener(client -> {
System.out.println("Connected: " + client.getSessionId());
// Join room via query param: ?room=room1, verify room membership if needed
String room = client.getHandshakeData()
.getSingleUrlParam("room");
if (room != null) {
client.joinRoom(room);
System.out.println("Joined room: " + room);
}
});
server.addDisconnectListener(client ->
System.out.println("Disconnected: " + client.getSessionId())
);
server.addEventListener(
"message",
String.class,
(SocketIOClient client, String data, var ack) -> {
System.out.println("Received: " + data);
// Broadcast to all clients
server.getBroadcastOperations()
.sendEvent("message", data);
ack.sendAckData("ok");
}
);
server.start();
System.out.println("SocketIO4J server started on :9092");
Runtime.getRuntime().addShutdownHook(
new Thread(server::stop)
);
}
}
```
{% endcode %}
{% endtab %}
{% endtabs %}
### Client
{% tabs %}
{% tab title="Java" %}
{% code title="Client.java
" overflow="wrap" expandable="true" %}
```java
//package com.socketio4j.examples.core;
import io.socket.client.IO;
import io.socket.client.Socket;
import java.net.URISyntaxException;
import java.util.Collections;
public class SocketIoClient {
public static void main(String[] args) throws URISyntaxException {
IO.Options options = new IO.Options();
options.query = "room=room1";
options.forceNew = true;
Socket socket = IO.socket("http://localhost:9092", options);
socket.on(Socket.EVENT_CONNECT, args1 -> {
System.out.println("Connected: " + socket.id());
socket.emit("message", "Hello from Java");
});
socket.on("message", args1 ->
System.out.println("Received: " + args1[0])
);
socket.connect();
}
}
```
{% endcode %}
{% endtab %}
{% tab title="node.js" %}
{% code title="client.js" overflow="wrap" expandable="true" %}
```javascript
import { io } from "socket.io-client";
const socket = io("http://localhost:9092", {
query: { room: "room1" }
});
socket.on("connect", () => {
console.log("Connected:", socket.id);
socket.emit("message", "Hello from Node.js");
});
socket.on("message", (data) => {
console.log("Received:", data);
});
```
{% endcode %}
{% endtab %}
{% tab title="Dart / Flutter" %}
{% code overflow="wrap" expandable="true" %}
```dart
import 'package:socket_io_client/socket_io_client.dart' as IO;
void main() {
IO.Socket socket = IO.io(
'http://localhost:9092',
IO.OptionBuilder()
.setQuery({'room': 'room1'})
.setTransports(['websocket'])
.build(),
);
socket.onConnect((_) {
print('Connected: ${socket.id}');
socket.emit('message', 'Hello from Dart');
});
socket.on('message', (data) {
print('Received: $data');
});
}
```
{% endcode %}
{% endtab %}
{% tab title="Swift (iOS)" %}
{% code overflow="wrap" expandable="true" %}
```swift
import SocketIO
let manager = SocketManager(
socketURL: URL(string: "http://localhost:9092")!,
config: [.log(true), .connectParams(["room": "room1"])]
)
let socket = manager.defaultSocket
socket.on(clientEvent: .connect) { _, _ in
print("Connected:", socket.sid ?? "")
socket.emit("message", "Hello from Swift")
}
socket.on("message") { data, _ in
print("Received:", data[0])
}
socket.connect()
```
{% endcode %}
{% endtab %}
{% tab title="Browser - Vanilla JS" %}
{% code overflow="wrap" expandable="true" %}
```html
```
{% endcode %}
{% endtab %}
{% tab title="Python" %}
{% code title="client.py" overflow="wrap" expandable="true" %}
```py
import socketio
sio = socketio.Client()
@sio.event
def connect():
print("Connected:", sio.sid)
sio.emit("message", "Hello from Python")
@sio.on("message")
def on_message(data):
print("Received:", data)
sio.connect("http://localhost:9092?room=room1")
sio.wait()
```
{% endcode %}
{% endtab %}
{% tab title="C# (.NET)" %}
{% code overflow="wrap" expandable="true" %}
```csharp
using SocketIOClient;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
class Program
{
static async Task Main()
{
var client = new SocketIO("http://localhost:9092", new SocketIOOptions
{
Query = new[] {
new KeyValuePair("room", "room1")
}
});
client.OnConnected += async (sender, e) =>
{
Console.WriteLine($"Connected: {client.Id}");
await client.EmitAsync("message", "Hello from C#");
};
client.On("message", response =>
{
Console.WriteLine("Received: " + response.GetValue());
});
await client.ConnectAsync();
await Task.Delay(-1);
}
}
```
{% endcode %}
{% endtab %}
{% tab title="Go" %}
{% code overflow="wrap" expandable="true" %}
```go
package main
import (
"fmt"
socketio "github.com/zhouhui8915/go-socket.io-client"
)
func main() {
opts := &socketio.Options{
Query: map[string]string{
"room": "room1",
},
}
client, err := socketio.NewClient("http://localhost:9092", opts)
if err != nil {
panic(err)
}
client.On("connect", func() {
fmt.Println("Connected")
client.Emit("message", "Hello from Go")
})
client.On("message", func(msg string) {
fmt.Println("Received:", msg)
})
select {}
}
```
{% endcode %}
{% endtab %}
{% tab title="Rust" %}
{% code overflow="wrap" expandable="true" %}
```rs
use rust_socketio::{ClientBuilder, Payload};
fn main() {
let client = ClientBuilder::new("http://localhost:9092")
.query("room", "room1")
.on("connect", |_, _| {
println!("Connected");
})
.on("message", |payload, _| {
if let Payload::String(msg) = payload {
println!("Received: {}", msg);
}
})
.connect()
.expect("Connection failed");
client.emit("message", "Hello from Rust").unwrap();
loop {}
}
```
{% endcode %}
{% endtab %}
{% endtabs %}
Join a growing community, built on a foundation trusted by 7,000+ developers
Join our Discord community or create your first PR in just a few steps.
| | | | Cover image |
|---|
:discord: | Discord community | Join our Discord community to post questions, get help, and share resources with over 7,000+ like-minded curious developer community. | Join Discord | |
:github: | GitHub | Our product is 100% open source and built by developers just like you. Head to our GitHub repository to learn how to submit your first PR. | Submit a PR | |
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.
Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:
```
GET https://www.socketio4j.org/home.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
