Connect Handler

Last updated Oct 13, 2026

Background

Export a connect() handler to let a Worker accept an inbound TCP connection and read and write raw bytes on it. The handler receives a Socket object, the same type returned by connect() from cloudflare:sockets for outbound connections.

A Worker receives a connection in its connect() handler when another Worker forwards a TCP connection to it over a service binding, by calling connect() on the binding:

// Worker A forwards a TCP connection to Worker B over a service binding
export default {
    async fetch(request, env) {
        const socket = env.BACKEND.connect("example.com:1234");
        // Read from and write to socket.readable / socket.writable
        return new Response(socket.readable);
    },
};

Note

Direct inbound TCP connections from the public Internet, for example by using the HTTP CONNECT method against a Worker's public URL, are not supported at present. A connect() handler only receives connections forwarded from another Worker over a service binding.

Syntax

export default {
    async connect(socket, env, ctx) {
        const writer = socket.writable.getWriter();
        await writer.write(new TextEncoder().encode("hello"));
        await writer.close();
    },
};

interface Env {}

export default {
    async connect(socket: Socket, env: Env, ctx: ExecutionContext) {
        const writer = socket.writable.getWriter();
        await writer.write(new TextEncoder().encode("hello"));
        await writer.close();
    },
} satisfies ExportedHandler<Env>;

You can also implement connect() as a method on a WorkerEntrypoint class, which lets a single Worker expose a connect() handler alongside other RPC methods:

import { WorkerEntrypoint } from "cloudflare:workers";

export class Backend extends WorkerEntrypoint {
    async connect(socket) {
        const writer = socket.writable.getWriter();
        await writer.write(new TextEncoder().encode("hello"));
        await writer.close();
    }
}

Parameters

• socket Socket
• The inbound Socket used to read and write raw bytes on the connection.
• socket.opened resolves with a SocketInfo object. On a connect() handler, localAddress is set to the address the caller passed to connect() on the service binding.
• env object
• The bindings available to the Worker.
• ctx object
• The context associated with the Worker, containing waitUntil() and passThroughOnException().

A Worker that does not export a connect() handler rejects any connection forwarded to it.

Related resources

• TCP sockets — Create outbound TCP connections and work with the Socket API.
• Service bindings — Call one Worker from another, including forwarding TCP connections with connect().

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