Version 0.1 alpha
Quick and dirty implementation of WebSocket server.
For testing purposes only.
websocket::Server server;
// listen on 0.0.0.0:8888
// log errors to stderr
server.start("0.0.0.0", 8888, std::cerr);
...
// check for a new event
websocket::Event event;
websocket::ConnectionId connId;
std::string message;
if (server.poll(event, connId, message) {
switch (event) {
case websocket::Event::NewConnection:
std::cout << '#' << connId << " connected\n";
break;
case websocket::Event::Message:
std::cout << '#' << connId << " says " << message << '\n';
// send reply
server.send(connId, message);
break;
case websocket::Event::Disconnect:
std::cout << '#' << connId << " disconnected\n";
break;
}
}
...
// stop server
server.stop();
// destructor also can call stop(), but it's better to do it explicitly
- Fragmented messages are not supported
- Client can't send a message longer than 125 bytes
- Server can't send a message longer than UINT32_MAX bytes
- Server doesn't validate client text frames.
Client sends HTTP GET request
GET /some/path/with/optional?query HTTP/1.1
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Version: 13
... other fields ...
Server replies with
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
and then they send data frames for each other
Data frames from client looks like this:
XX YY [LL LL | LL LL LL LL LL LL LL LL] KK KK KK KK [data]
where
XX- byte with opcode and the "final fragment" flag, 0x81 for non-fragmented text frame.YY- byte with data length, high bit is set to 1, i.e. 0x85 for 5-byte data.
If length is 126, next two bytes are real 16-bit length. If length is 127, next eight bytes are real 64-bit length.KK- four bytes of the masking keydata- data bytes XORed with the masking key,data[i] ^ key[i % 4].
Example:
81 85 F0 F0 F0 F0 C1 C2 C3 C4 C5 -- text "12345"
Almost like client frames, but without masking.
XX LL [LL LL | LL LL LL LL LL LL LL LL] [data]
XX- opcode and "final fragment" flag.LL- data length (0 - 125), 126 and 127 for extended length.data- data bytes.
Example:
81 05 31 32 33 34 35 -- text "12345"
websocket-cpp is placed in the public domain.
- RFC 6455 - The WebSocket Protocol