WebSocket

Overview

rust-web-server includes a complete WebSocket implementation in src/websocket/mod.rs. It covers upgrade detection, the RFC 6455 opening handshake (SHA-1 + base64 key derivation), and frame-level read/write for all standard opcodes.

Integration pattern

WebSocket connections require taking over the raw TCP stream after the 101 upgrade response. They are handled in a custom accept loop rather than through the normal Controller / Application pipeline (which has no access to the underlying stream).

use std::net::TcpListener;
use rust_web_server::request::Request;
use rust_web_server::websocket::{WebSocket, Frame};

let listener = TcpListener::bind("127.0.0.1:7878").unwrap();

for stream in listener.incoming() {
    let mut stream = stream.unwrap();

    // Read the HTTP upgrade request.
    let mut buf = vec![0u8; 4096];
    let n = stream.read(&mut buf).unwrap();
    let request = Request::parse(&buf[..n]).unwrap();

    if WebSocket::is_upgrade_request(&request) {
        // Send 101 Switching Protocols.
        let response = WebSocket::handshake_response(&request).unwrap();
        stream.write_all(&response.generate_response()).unwrap();

        // Enter the frame loop.
        loop {
            match WebSocket::read_frame(&mut stream) {
                Ok(Frame::Text(msg)) => {
                    WebSocket::write_frame(&mut stream, Frame::Text(msg)).unwrap();
                }
                Ok(Frame::Ping(data)) => {
                    WebSocket::write_frame(&mut stream, Frame::Pong(data)).unwrap();
                }
                Ok(Frame::Close(code, reason)) => {
                    WebSocket::send_close(&mut stream, code.unwrap_or(1000), &reason).ok();
                    break;
                }
                Ok(_) => {}
                Err(_) => break,
            }
        }
    }
}

Detecting upgrade requests

WebSocket::is_upgrade_request(request: &Request) -> bool

Returns true when the request has all three required headers:

Upgrade: websocket
Connection: Upgrade (or any value containing “upgrade”)
Sec-WebSocket-Key: <base64>

Handshake response

WebSocket::handshake_response(request: &Request) -> Result<Response, String>

Builds an HTTP 101 Switching Protocols response with the correct Sec-WebSocket-Accept value. The accept value is computed as:

base64(SHA-1(client_key + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"))

Both SHA-1 and base64 are implemented from scratch in src/websocket/mod.rs with no external dependencies.

If the request includes a Sec-WebSocket-Protocol header, the first listed sub-protocol is echoed back in the response.

Frame types

Frame is an enum covering all RFC 6455 opcodes:

Variant	Opcode	Description
`Frame::Text(String)`	`0x1`	A complete UTF-8 text message
`Frame::Binary(Vec<u8>)`	`0x2`	A binary message
`Frame::Ping(Vec<u8>)`	`0x9`	Ping — respond with a matching Pong
`Frame::Pong(Vec<u8>)`	`0xA`	Pong
`Frame::Close(Option<u16>, String)`	`0x8`	Close with optional status code and reason
`Frame::Continuation { fin, data }`	`0x0`	Continuation fragment for fragmented messages

Reading frames

WebSocket::read_frame(stream: &mut impl Read) -> Result<Frame, String>

Reads one complete frame. Client-to-server masking (required by RFC 6455) is handled automatically — the payload is unmasked before being returned. Extended payload lengths (16-bit and 64-bit) are supported.

Writing frames

WebSocket::write_frame(stream: &mut impl Write, frame: Frame) -> Result<(), String>

Writes one frame. Server-to-client frames are sent unmasked per the RFC. Payload length encoding (7-bit, 16-bit, 64-bit) is chosen automatically.

Convenience methods

// Send a text message
WebSocket::send_text(&mut stream, "hello")?;

// Send a close frame
WebSocket::send_close(&mut stream, 1000, "normal closure")?;

// Reply to a Ping with a Pong
WebSocket::send_pong(&mut stream, ping_payload)?;

Complete echo server example

use std::net::TcpListener;
use std::io::Read;
use rust_web_server::request::Request;
use rust_web_server::websocket::{WebSocket, Frame};

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
    println!("WebSocket echo server listening on ws://127.0.0.1:7878");

    for stream in listener.incoming() {
        std::thread::spawn(|| {
            let mut stream = stream.unwrap();
            let mut buf = vec![0u8; 4096];
            let n = stream.read(&mut buf).unwrap();

            let request = Request::parse(&buf[..n]).unwrap();
            if !WebSocket::is_upgrade_request(&request) { return; }

            let handshake = WebSocket::handshake_response(&request).unwrap();
            use std::io::Write;
            stream.write_all(&handshake.generate_response()).unwrap();

            loop {
                match WebSocket::read_frame(&mut stream) {
                    Ok(Frame::Text(msg)) => {
                        WebSocket::write_frame(&mut stream, Frame::Text(msg)).unwrap();
                    }
                    Ok(Frame::Binary(data)) => {
                        WebSocket::write_frame(&mut stream, Frame::Binary(data)).unwrap();
                    }
                    Ok(Frame::Ping(data)) => {
                        WebSocket::send_pong(&mut stream, data).unwrap();
                    }
                    Ok(Frame::Close(code, reason)) => {
                        WebSocket::send_close(&mut stream, code.unwrap_or(1000), &reason).ok();
                        break;
                    }
                    _ => break,
                }
            }
        });
    }
}