1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3SPDX-License-Identifier: curl 4Title: curl_easy_recv 5Section: 3 6Source: libcurl 7See-also: 8 - curl_easy_getinfo (3) 9 - curl_easy_perform (3) 10 - curl_easy_send (3) 11 - curl_easy_setopt (3) 12Protocol: 13 - All 14Added-in: 7.18.2 15--- 16 17# NAME 18 19curl_easy_recv - receives raw data on an "easy" connection 20 21# SYNOPSIS 22 23~~~c 24#include <curl/curl.h> 25 26CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n); 27~~~ 28 29# DESCRIPTION 30 31This function receives raw data from the established connection. You may use 32it together with curl_easy_send(3) to implement custom protocols using 33libcurl. This functionality can be particularly useful if you use proxies 34and/or SSL encryption: libcurl takes care of proxy negotiation and connection 35setup. 36 37**buffer** is a pointer to your buffer memory that gets populated by the 38received data. **buflen** is the maximum amount of data you can get in that 39buffer. The variable **n** points to receives the number of received bytes. 40 41To establish the connection, set CURLOPT_CONNECT_ONLY(3) option before 42calling curl_easy_perform(3) or curl_multi_perform(3). Note that 43curl_easy_recv(3) does not work on connections that were created without 44this option. 45 46The call returns **CURLE_AGAIN** if there is no data to read - the socket is 47used in non-blocking mode internally. When **CURLE_AGAIN** is returned, use 48your operating system facilities like *select(2)* to wait for data. The 49socket may be obtained using curl_easy_getinfo(3) with 50CURLINFO_ACTIVESOCKET(3). 51 52Wait on the socket only if curl_easy_recv(3) returns **CURLE_AGAIN**. 53The reason for this is libcurl or the SSL library may internally cache some 54data, therefore you should call curl_easy_recv(3) until all data is 55read which would include any cached data. 56 57Furthermore if you wait on the socket and it tells you there is data to read, 58curl_easy_recv(3) may return **CURLE_AGAIN** if the only data that was 59read was for internal SSL processing, and no other data is available. 60 61# %PROTOCOLS% 62 63# EXAMPLE 64 65~~~c 66int main(void) 67{ 68 CURL *curl = curl_easy_init(); 69 if(curl) { 70 CURLcode res; 71 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com"); 72 /* Do not do the transfer - only connect to host */ 73 curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L); 74 res = curl_easy_perform(curl); 75 76 if(res == CURLE_OK) { 77 char buf[256]; 78 size_t nread; 79 long sockfd; 80 81 /* Extract the socket from the curl handle - we need it for waiting. */ 82 res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd); 83 84 /* read data */ 85 res = curl_easy_recv(curl, buf, sizeof(buf), &nread); 86 } 87 } 88} 89~~~ 90 91# %AVAILABILITY% 92 93# RETURN VALUE 94 95On success, returns **CURLE_OK**, stores the received data into 96**buffer**, and the number of bytes it actually read into ***n**. 97 98On failure, returns the appropriate error code. 99 100The function may return **CURLE_AGAIN**. In this case, use your operating 101system facilities to wait until data can be read, and retry. 102 103Reading exactly 0 bytes indicates a closed connection. 104 105If there is no socket available to use from the previous transfer, this function 106returns **CURLE_UNSUPPORTED_PROTOCOL**. 107
