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",
 (unsigned int)rlen);
 }
 else {
 /* some other frame arrived. */
 fprintf(stderr, "ws: received frame of %u bytes rflags %x\n",
 (unsigned 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_global_init(CURL_GLOBAL_ALL);
 if(res)
 return (int)res;
 
 curl = curl_easy_init();
 if(curl) {
 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);
 }
 curl_global_cleanup();
 return (int)res;
}

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