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curl_easy_recv(3)                   libcurl                  curl_easy_recv(3)


curl_easy_recv - receives raw data on an "easy" connection


#include <curl/easy.h> CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n);


This function receives raw data from the established connection. You may use it together with curl_easy_send(3) 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. buffer is a pointer to your buffer that will get the received data. buflen is the maximum amount of data you can get in that buffer. The variable n points to will receive the number of received bytes. To establish the connection, set CURLOPT_CONNECT_ONLY(3) option before calling curl_easy_perform(3) or curl_multi_perform(3). Note that curl_easy_recv(3) does not work on connections that were created without this option. The call will return CURLE_AGAIN if there is no data to read - the socket is used in non-blocking mode internally. When CURLE_AGAIN is returned, use your operating system facilities like select(2) to wait for data. The socket may be obtained using curl_easy_getinfo(3) with CURLINFO_ACTIVESOCKET(3). Wait on the socket only if curl_easy_recv(3) returns CURLE_AGAIN. The reason for this is libcurl or the SSL library may internally cache some data, therefore you should call curl_easy_recv(3) 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, curl_easy_recv(3) may return CURLE_AGAIN if the only data that was read was for internal SSL processing, and no other data is available.


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); }


Added in 7.18.2.


On success, returns CURLE_OK, stores the received data into buffer, and the number of bytes it actually read into *n. On failure, returns the appropriate error code. The function may return CURLE_AGAIN. 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 CURLE_UNSUPPORTED_PROTOCOL.


curl_easy_setopt(3), curl_easy_perform(3), curl_easy_getinfo(3), curl_easy_send(3) libcurl 8.1.2 April 26, 2023 curl_easy_recv(3)

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