examples/websocket.c: websocket example using CONNECT_ONLY

Closes #11262

docs/examples/Makefile.inc

@@ -118,6 +118,7 @@ check_PROGRAMS = \
   sslbackend \
   url2file \
   urlapi \
+  websocket \
   websocket-cb
 
 # These examples require external dependencies that may not be commonly

docs/examples/websocket.c

@@ -0,0 +1,131 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  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>
+#include <unistd.h>
+#include <curl/curl.h>
+
+static int ping(CURL *curl, const char *send_payload)
+{
+  size_t sent;
+  CURLcode result =
+    curl_ws_send(curl, send_payload, strlen(send_payload), &sent, 0,
+                 CURLWS_PING);
+  return (int)result;
+}
+
+static int recv_pong(CURL *curl, const char *exected_payload)
+{
+  size_t rlen;
+  struct curl_ws_frame *meta;
+  char buffer[256];
+  CURLcode result = curl_ws_recv(curl, buffer, sizeof(buffer), &rlen, &meta);
+  if(!result) {
+    if(meta->flags & CURLWS_PONG) {
+      int same = 0;
+      fprintf(stderr, "ws: got PONG back\n");
+      if(rlen == strlen(exected_payload)) {
+        if(!memcmp(exected_payload, buffer, rlen)) {
+          fprintf(stderr, "ws: got the same payload back\n");
+          same = 1;
+        }
+      }
+      if(!same)
+        fprintf(stderr, "ws: did NOT get the same payload back\n");
+    }
+    else {
+      fprintf(stderr, "recv_pong: got %u bytes rflags %x\n", (int)rlen,
+              meta->flags);
+    }
+  }
+  fprintf(stderr, "ws: curl_ws_recv returned %u, received %u\n",
+          (unsigned int)result, (unsigned int)rlen);
+  return (int)result;
+}
+
+static int recv_any(CURL *curl)
+{
+  size_t rlen;
+  struct curl_ws_frame *meta;
+  char buffer[256];
+  CURLcode result = curl_ws_recv(curl, buffer, sizeof(buffer), &rlen, &meta);
+  if(result)
+    return result;
+
+  return 0;
+}
+
+/* close the connection */
+static void websocket_close(CURL *curl)
+{
+  size_t sent;
+  (void)curl_ws_send(curl, "", 0, &sent, 0, CURLWS_CLOSE);
+}
+
+static void websocket(CURL *curl)
+{
+  int i = 0;
+  do {
+    recv_any(curl);
+    if(ping(curl, "foobar"))
+      return;
+    if(recv_pong(curl, "foobar")) {
+      return;
+    }
+    sleep(2);
+  } while(i++ < 10);
+  websocket_close(curl);
+}
+
+int main(void)
+{
+  CURL *curl;
+  CURLcode res;
+
+  curl = curl_easy_init();
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "wss://example.com");
+
+    curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 2L); /* websocket style */
+
+    /* Perform the request, res will get 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 */
+      websocket(curl);
+    }
+
+    /* always cleanup */
+    curl_easy_cleanup(curl);
+  }
+  return 0;
+}