Limitations

Client

The client doesn’t attempt to guarantee that there is no more than one connection to a given IP address in a CONNECTING state. This behavior is mandated by RFC 6455. However, connect() isn’t the right layer for enforcing this constraint. It’s the caller’s responsibility.

The client doesn’t support connecting through a HTTP proxy (issue 364) or a SOCKS proxy (issue 475).

Server

At this time, there are no known limitations affecting only the server.

Both sides

There is no way to control compression of outgoing frames on a per-frame basis (issue 538). If compression is enabled, all frames are compressed.

There is no way to receive each fragment of a fragmented messages as it arrives (issue 479). websockets always reassembles fragmented messages before returning them.