websocket-updown.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 download-only using write callback
 * </DESC>
 */
#include <stdio.h>
#include <string.h>
 
#include <curl/curl.h>
 
static size_t write_cb(char *b, size_t size, size_t nitems, void *p)
{
  CURL *curl = p;
  size_t i;
  unsigned int blen = (unsigned int)(nitems * size);
  const struct curl_ws_frame *frame = curl_ws_meta(curl);
  fprintf(stderr, "Type: %s\n",
          frame->flags & CURLWS_BINARY ? "binary" : "text");
  if(frame->flags & CURLWS_BINARY) {
    fprintf(stderr, "Bytes: %u", blen);
    for(i = 0; i < nitems; i++)
      fprintf(stderr, "%02x ", (unsigned char)b[i]);
    fprintf(stderr, "\n");
  }
  else
    fprintf(stderr, "Text: %.*s\n", (int)blen, b);
  return nitems;
}
 
struct read_ctx {
  CURL *curl;
  char buf[1024];
  size_t blen;
  size_t nsent;
};
 
static size_t read_cb(char *buf, size_t nitems, size_t buflen, void *p)
{
  struct read_ctx *ctx = p;
  size_t len = nitems * buflen;
  size_t left = ctx->blen - ctx->nsent;
 
  if(!ctx->nsent) {
    CURLcode result;
    /* On first call, set the FRAME information to be used (it defaults to
     * CURLWS_BINARY otherwise). */
    result = curl_ws_start_frame(ctx->curl, CURLWS_TEXT,
                                 (curl_off_t)ctx->blen);
    if(result != CURLE_OK) {
      fprintf(stderr, "error starting frame: %d\n", (int)result);
      return CURL_READFUNC_ABORT;
    }
  }
  fprintf(stderr, "read(len=%d, left=%d)\n", (int)len, (int)left);
  if(left) {
    if(left < len)
      len = left;
    memcpy(buf, ctx->buf + ctx->nsent, len);
    ctx->nsent += len;
    return len;
  }
  return 0;
}
 
int main(int argc, const char *argv[])
{
  CURL *curl;
  struct read_ctx rctx;
  const char *payload = "Hello, friend!";
 
  CURLcode result = curl_global_init(CURL_GLOBAL_ALL);
  if(result != CURLE_OK)
    return (int)result;
 
  memset(&rctx, 0, sizeof(rctx));
 
  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_WRITEFUNCTION, write_cb);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, curl);
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_cb);
    /* tell curl that we want to send the payload */
    rctx.curl = curl;
    rctx.blen = strlen(payload);
    memcpy(rctx.buf, payload, rctx.blen);
    curl_easy_setopt(curl, CURLOPT_READDATA, &rctx);
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
 
    /* Perform the request, result gets the return code */
    result = curl_easy_perform(curl);
    /* Check for errors */
    if(result != CURLE_OK)
      fprintf(stderr, "curl_easy_perform() failed: %s\n",
              curl_easy_strerror(result));
 
    /* always cleanup */
    curl_easy_cleanup(curl);
  }
  curl_global_cleanup();
  return (int)result;
}

Notice