libdill: Structured Concurrency for C


ws_recv - receives a WebSocket message


#include <libdill.h>

ssize_t ws_recv(
    int s,
    int* flags,
    void* buf,
    size_t len,
    int64_t deadline);


WARNING: This is experimental functionality and the API may change in the future.

WebSocket is a message-based protocol defined in RFC 6455. It can be used as a bidirectional communication channel for communication with a web server.

This function receives one WebSocket message. It is very much the same as mrecv except that it returns the type of the message (either text or binary).

s: The socket handle.

flags: Out parameter. Possible values are either WS_BINARYor WS_TEXT.

buf: Buffer to receive the data to.

len: Size of the buffer, in bytes.

deadline: A point in time when the operation should time out, in milliseconds. Use the now function to get your current point in time. 0 means immediate timeout, i.e., perform the operation if possible or return without blocking if not. -1 means no deadline, i.e., the call will block forever if the operation cannot be performed.

This function is not available if libdill is compiled with --disable-sockets option.


In case of success the function returns size of the received message, in bytes. In case of error it returns -1 and sets errno to one of the values below.



struct ipaddr addr;
ipaddr_remote(&addr, "", 80, 0, -1);
int s = tcp_connect(&addr, -1);
s = ws_attach_client(s, "/", "", WS_TEXT, -1);
ws_send(s, WS_TEXT, "Hello, world!", 13, -1);
int flags;
char buf[256];
ssize_t sz = ws_recv(s, &flags, buf, sizeof(buf), -1);
assert(flags & WS_TEXT);
s = ws_detach(s, -1);
tcp_close(s, -1);


mrecv(3) mrecvl(3) msend(3) msendl(3) now(3) ws_attach_client(3) ws_attach_client_mem(3) ws_attach_server(3) ws_attach_server_mem(3) ws_detach(3) ws_recvl(3) ws_request_key(3) ws_response_key(3) ws_send(3) ws_sendl(3)