endpoint WebSocketClient
{
    // Connection API
    connected(i32 connection_id) =|
    received(i32 connection_id, bool is_text, ByteBuffer data) =|
    errored(i32 connection_id, i32 message) =|
    closed(i32 connection_id, u16 code, String reason, bool clean) =|

    // Certificate requests
    certificate_requested(i32 connection_id) =|
}