e3fe020089
Remove the PROTOCOLS section from the source files completely and instead generate them based on the header data in the curldown files. It also generates TLS backend information for options marked for TLS as protocol. Closes #13175
106 lines
3.1 KiB
Markdown
106 lines
3.1 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.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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Protocol:
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- All
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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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