104 lines
3.1 KiB
Markdown
104 lines
3.1 KiB
Markdown
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c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
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SPDX-License-Identifier: curl
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Title: curl_easy_recv
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Section: 3
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Source: libcurl
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See-also:
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- curl_easy_getinfo (3)
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- curl_easy_perform (3)
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- curl_easy_send (3)
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- curl_easy_setopt (3)
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---
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# NAME
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curl_easy_recv - receives raw data on an "easy" connection
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n);
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~~~
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# DESCRIPTION
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This function receives raw data from the established connection. You may use
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it together with curl_easy_send(3) to implement custom protocols using
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libcurl. This functionality can be particularly useful if you use proxies
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and/or SSL encryption: libcurl takes care of proxy negotiation and connection
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setup.
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**buffer** is a pointer to your buffer memory that gets populated by the
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received data. **buflen** is the maximum amount of data you can get in that
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buffer. The variable **n** points to receives the number of received bytes.
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To establish the connection, set CURLOPT_CONNECT_ONLY(3) option before
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calling curl_easy_perform(3) or curl_multi_perform(3). Note that
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curl_easy_recv(3) does not work on connections that were created without
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this option.
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The call returns **CURLE_AGAIN** if there is no data to read - the socket is
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used in non-blocking mode internally. When **CURLE_AGAIN** is returned, use
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your operating system facilities like *select(2)* to wait for data. The
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socket may be obtained using curl_easy_getinfo(3) with
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CURLINFO_ACTIVESOCKET(3).
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Wait on the socket only if curl_easy_recv(3) returns **CURLE_AGAIN**.
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The reason for this is libcurl or the SSL library may internally cache some
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data, therefore you should call curl_easy_recv(3) until all data is
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read which would include any cached data.
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Furthermore if you wait on the socket and it tells you there is data to read,
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curl_easy_recv(3) may return **CURLE_AGAIN** if the only data that was
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read was for internal SSL processing, and no other data is available.
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# EXAMPLE
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~~~c
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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CURLcode res;
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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/* Do not do the transfer - only connect to host */
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curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
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res = curl_easy_perform(curl);
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if(res == CURLE_OK) {
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char buf[256];
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size_t nread;
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long sockfd;
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/* Extract the socket from the curl handle - we need it for waiting. */
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res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);
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/* read data */
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res = curl_easy_recv(curl, buf, sizeof(buf), &nread);
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}
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}
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}
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~~~
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# AVAILABILITY
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Added in 7.18.2.
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# RETURN VALUE
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On success, returns **CURLE_OK**, stores the received data into
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**buffer**, and the number of bytes it actually read into ***n**.
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On failure, returns the appropriate error code.
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The function may return **CURLE_AGAIN**. In this case, use your operating
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system facilities to wait until data can be read, and retry.
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Reading exactly 0 bytes indicates a closed connection.
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If there is no socket available to use from the previous transfer, this function
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returns **CURLE_UNSUPPORTED_PROTOCOL**.
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