.\" ************************************************************************** .\" * _ _ ____ _ .\" * Project ___| | | | _ \| | .\" * / __| | | | |_) | | .\" * | (__| |_| | _ <| |___ .\" * \___|\___/|_| \_\_____| .\" * .\" * Copyright (C) Daniel Stenberg, , 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 .\" * .\" ************************************************************************** .\" .TH curl_easy_recv 3 "January 02, 2023" "libcurl 7.88.1" "libcurl Manual" .SH NAME curl_easy_recv - receives raw data on an "easy" connection .SH SYNOPSIS .nf #include CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n); .fi .SH DESCRIPTION This function receives raw data from the established connection. You may use it together with \fIcurl_easy_send(3)\fP to implement custom protocols using libcurl. This functionality can be particularly useful if you use proxies and/or SSL encryption: libcurl will take care of proxy negotiation and connection setup. \fBbuffer\fP is a pointer to your buffer that will get the received data. \fBbuflen\fP is the maximum amount of data you can get in that buffer. The variable \fBn\fP points to will receive the number of received bytes. To establish the connection, set \fICURLOPT_CONNECT_ONLY(3)\fP option before calling \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP. Note that \fIcurl_easy_recv(3)\fP does not work on connections that were created without this option. The call will return \fBCURLE_AGAIN\fP if there is no data to read - the socket is used in non-blocking mode internally. When \fBCURLE_AGAIN\fP is returned, use your operating system facilities like \fIselect(2)\fP to wait for data. The socket may be obtained using \fIcurl_easy_getinfo(3)\fP with \fICURLINFO_ACTIVESOCKET(3)\fP. Wait on the socket only if \fIcurl_easy_recv(3)\fP returns \fBCURLE_AGAIN\fP. The reason for this is libcurl or the SSL library may internally cache some data, therefore you should call \fIcurl_easy_recv(3)\fP until all data is read which would include any cached data. Furthermore if you wait on the socket and it tells you there is data to read, \fIcurl_easy_recv(3)\fP may return \fBCURLE_AGAIN\fP if the only data that was read was for internal SSL processing, and no other data is available. .SH EXAMPLE .nf curl_easy_setopt(curl, CURLOPT_URL, "https://example.com"); /* Do not do the transfer - only connect to host */ curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L); res = curl_easy_perform(curl); if(res == CURLE_OK) { /* Extract the socket from the curl handle - we will need it for waiting. */ res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd); /* read data */ res = curl_easy_recv(curl, buf, sizeof(buf), &nread); } .fi .SH AVAILABILITY Added in 7.18.2. .SH RETURN VALUE On success, returns \fBCURLE_OK\fP, stores the received data into \fBbuffer\fP, and the number of bytes it actually read into \fB*n\fP. On failure, returns the appropriate error code. The function may return \fBCURLE_AGAIN\fP. In this case, use your operating system facilities to wait until data can be read, and retry. Reading exactly 0 bytes indicates a closed connection. If there's no socket available to use from the previous transfer, this function returns \fBCURLE_UNSUPPORTED_PROTOCOL\fP. .SH "SEE ALSO" .BR curl_easy_setopt "(3), " curl_easy_perform "(3), " .BR curl_easy_getinfo "(3), " .BR curl_easy_send "(3) "