libdill: Structured Concurrency for C

NAME

ws_response_key - generates a WebSocket response key for a given request key

SYNOPSIS

#include <libdill.h>

int ws_response_key(
    const char* request_key,
    char* response_key);

DESCRIPTION

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 is a helper function that can be used when doing a custom HTTP handshake for the WebSocket protocol (see WS_NOHTTP flag). On the server, it can be used to generates an RFC-compliant response key, to be filled into Sec-WebSocket-Accept field, for a request key received from the client. On the client side, it can be used to verify that the response key received from the server is correct.

The generated key is null-terminated.

request_key: The request key, as passed in Sec-WebSocket-Key field.

response_key: Buffer to hold the generated response key. It must be at least WS_KEY_SIZE bytes long.

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

RETURN VALUE

In case of success the function returns 0. In case of error it returns -1 and sets errno to one of the values below.

ERRORS

EINVAL: Invalid argument.
EPROTO: Supplied request key is not RFC 6455 compliant.

EXAMPLE

char name[256];
char value[256];
http_recvfield(s, name, sizeof(name), value, sizeof(value), -1);
assert(strcasecmp(name, "Sec-WebSocket-Key") == 0);
ws_response_key(value, response_key);
http_sendfield(s, "Sec-WebSocket-Accept", response_key, -1);