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