websocket.c
/*************************************************************************** * _ _ ____ _ * Project ___| | | | _ \| | * / __| | | | |_) | | * | (__| |_| | _ <| |___ * \___|\___/|_| \_\_____| * * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. * * This software is licensed as described in the file COPYING, which * you should have received as part of this distribution. The terms * are also available at https://curl.se/docs/copyright.html. * * You may opt to use, copy, modify, merge, publish, distribute and/or sell * copies of the Software, and permit persons to whom the Software is * furnished to do so, under the terms of the COPYING file. * * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY * KIND, either express or implied. * * SPDX-License-Identifier: curl * ***************************************************************************/ /* <DESC> * WebSocket using CONNECT_ONLY * </DESC> */ #include <stdio.h> #include <string.h> #ifdef _WIN32 #include <winsock2.h> #include <windows.h> #define sleep(s) Sleep((DWORD)(s)) #else #include <unistd.h> #endif #include <curl/curl.h> static CURLcode ping(CURL *curl, const char *send_payload) { CURLcode res = CURLE_OK; const char *buf = send_payload; size_t sent, blen = strlen(send_payload); while(blen) { res = curl_ws_send(curl, buf, blen, &sent, 0, CURLWS_PING); if(!res) { buf += sent; /* deduct what was sent */ blen -= sent; } else if(res == CURLE_AGAIN) { /* blocked on sending */ fprintf(stderr, "ws: sent PING blocked, waiting a second\n"); sleep(1); /* either select() on socket or max timeout would be good here. */ } else /* real error sending */ break; } if(!res) fprintf(stderr, "ws: sent PING with payload\n"); return res; } static CURLcode recv_pong(CURL *curl, const char *expected_payload) { size_t rlen; const struct curl_ws_frame *meta; char buffer[256]; CURLcode res; retry: res = curl_ws_recv(curl, buffer, sizeof(buffer), &rlen, &meta); if(!res) { /* on small PING content, this example assumes the complete * PONG content arrives in one go. Larger frames will arrive * in chunks, however. */ if(meta->flags & CURLWS_PONG) { int same = 0; if(rlen == strlen(expected_payload)) { if(!memcmp(expected_payload, buffer, rlen)) same = 1; } fprintf(stderr, "ws: received PONG with %s payload back\n", same ? "same" : "different"); } else if(meta->flags & CURLWS_TEXT) { fprintf(stderr, "ws: received TEXT frame '%.*s'\n", (int)rlen, buffer); } else if(meta->flags & CURLWS_BINARY) { fprintf(stderr, "ws: received BINARY frame of %u bytes\n", (int)rlen); } else { /* some other frame arrived. */ fprintf(stderr, "ws: received frame of %u bytes rflags %x\n", (int)rlen, meta->flags); goto retry; } } else if(res == CURLE_AGAIN) { /* blocked on receiving */ fprintf(stderr, "ws: PONG not there yet, waiting a second\n"); sleep(1); /* either select() on socket or max timeout would be good here. */ goto retry; } if(res) fprintf(stderr, "ws: curl_ws_recv returned %u, received %u\n", (unsigned int)res, (unsigned int)rlen); return res; } /* close the connection */ static void websocket_close(CURL *curl) { size_t sent; (void)curl_ws_send(curl, "", 0, &sent, 0, CURLWS_CLOSE); } static CURLcode websocket(CURL *curl) { CURLcode res; int i = 0; do { res = ping(curl, "foobar"); if(res) break; res = recv_pong(curl, "foobar"); if(res) break; sleep(1); } while(i++ < 10); websocket_close(curl); return res; } int main(int argc, const char *argv[]) { CURL *curl; CURLcode res; curl = curl_easy_init(); if(!curl) { return 1; /* memory failure */ } if(argc == 2) curl_easy_setopt(curl, CURLOPT_URL, argv[1]); else curl_easy_setopt(curl, CURLOPT_URL, "wss://example.com"); curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 2L); /* websocket style */ /* Perform the request, res gets the return code */ res = curl_easy_perform(curl); /* Check for errors */ if(res != CURLE_OK) fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res)); else { /* connected and ready */ res = websocket(curl); } /* always cleanup */ curl_easy_cleanup(curl); return (int)res; }
Notice
This source code example is simplified and ignores return
codes and error checks to a large extent. We do this to highlight the libcurl
function calls and related options and reduce unrelated code.
A real-world application will of course properly check every return value and exit correctly at the first serious error.