RTSP

import { buildResponse, parseRequest, parseResponse, RtspClient } from '@corewire/airplay/rtsp';

AirPlay control and RAOP both speak RTSP. This entry point holds the client they build on and the parsers.

RtspClient

RtspClient is a Connection that sends requests with CSeq tracking and a response timeout, and serializes object bodies as binary plists. Its exchange() method is protected, so you extend the class and give it the requests your protocol needs.

import { RtspClient } from '@corewire/airplay/rtsp';
import { Context } from '@corewire/core/transport';

class InfoClient extends RtspClient {
    async info(): Promise<Response> {
        return await this.exchange('GET', '/info', {allowError: true});
    }
}

const client = new InfoClient(new Context('Living-Room.local'), '192.168.1.20', 7000);
await client.connect();

const response = await client.info();
console.log(response.status, response.headers.get('content-type'));

await client.disconnect();

exchange(method, path, options?) resolves a web Response. It rejects with TimeoutError when no response arrives in time, and with InvalidResponseError for a status that is not OK unless you set allowError.

Option	Meaning
body	A Buffer, a string, or an object that becomes a binary plist
contentType	Set automatically for object bodies
headers	Extra headers
allowError	Resolve instead of reject on a status that is not OK
protocol	RTSP/1.0 (default) or HTTP/1.1
timeout	Milliseconds; 6000 by default

Three more protected methods are the extension points: getDefaultHeaders() adds headers to every request, transformOutgoing() encrypts a formatted request, and transformIncoming() decrypts incoming data. The client keeps ciphertext and plaintext in separate buffers, so a partial TCP delivery never mixes them.

Parsing

parseRequest(buffer) and parseResponse(buffer) parse one message from the start of a buffer. They return null while the buffer is incomplete, so you can call them as TCP data arrives. The result says how many bytes it used (requestLength, responseLength). buildResponse(options) formats a response with Content-Length set.

import { buildResponse, parseRequest } from '@corewire/airplay/rtsp';

declare function write(data: Buffer): void;

let buffer = Buffer.alloc(0);

function onData(data: Buffer): void {
    buffer = Buffer.concat([buffer, data]);

    let request = parseRequest(buffer);

    while (request) {
        buffer = buffer.subarray(request.requestLength);
        write(buildResponse({status: 200, statusText: 'OK', headers: {CSeq: request.headers.CSeq}}));
        request = parseRequest(buffer);
    }
}