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curl_easy_recv(3) Library Functions Manual curl_easy_recv(3) NAME curl_easy_recv - receives raw data on an "easy" connection SYNOPSIS #include <curl/curl.h> CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n); DESCRIPTION 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 takes care of proxy negotiation and connec- tion setup. buffer is a pointer to your buffer memory that gets populated by the re- ceived data. buflen is the maximum amount of data you can get in that buffer. The variable n points to receives 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 returns 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_AC- TIVESOCKET(3). Wait on the socket only if curl_easy_recv(3) returns CURLE_AGAIN. The rea- son 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. PROTOCOLS This functionality affects all supported protocols EXAMPLE int main(void) { CURL *curl = curl_easy_init(); if(curl) { CURLcode result; 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); result = curl_easy_perform(curl); if(result == CURLE_OK) { char buf[256]; size_t nread; curl_socket_t sockfd; /* Extract the socket from the curl handle - we need it for waiting. */ result = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd); /* read data */ result = curl_easy_recv(curl, buf, sizeof(buf), &nread); } } } AVAILABILITY Added in curl 7.18.2 RETURN VALUE 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 sys- tem facilities to wait until data can be read, and retry. Reading exactly 0 bytes indicates a closed connection. If there is no socket available to use from the previous transfer, this function returns CURLE_UNSUPPORTED_PROTOCOL. SEE ALSO curl_easy_getinfo(3), curl_easy_perform(3), curl_easy_send(3), curl_easy_setopt(3) libcurl 2026-06-11 curl_easy_recv(3)
NAME | SYNOPSIS | DESCRIPTION | PROTOCOLS | EXAMPLE | AVAILABILITY | RETURN VALUE | SEE ALSO
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