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curl_easy_send(3) Library Functions Manual curl_easy_send(3) NAME curl_easy_send - sends raw data over an "easy" connection SYNOPSIS #include <curl/curl.h> CURLcode curl_easy_send(CURL *curl, const void *buffer, size_t buflen, size_t *n); DESCRIPTION This function sends arbitrary data over the established connection. You may use it together with curl_easy_recv(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 the data of length buflen that you want sent. The variable n points to receives the number of sent 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_send(3) does not work on connections that were created without this option. The call returns CURLE_AGAIN if it is not possible to send data right now - the socket is used in non-blocking mode internally. When CURLE_AGAIN is re- turned, use your operating system facilities like select(2) to wait until the socket is writable. The socket may be obtained using curl_easy_get- info(3) with CURLINFO_ACTIVESOCKET(3). Furthermore if you wait on the socket and it tells you it is writable, curl_easy_send(3) may return CURLE_AGAIN if the only data that was sent was for internal SSL processing, and no other data could be sent. 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) { curl_socket_t sockfd; size_t sent; /* Extract the socket from the curl handle - we need it for waiting. */ result = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd); /* send data */ result = curl_easy_send(curl, "hello", 5, &sent); } } } AVAILABILITY Added in curl 7.18.2 RETURN VALUE On success, returns CURLE_OK and stores the number of bytes actually sent into *n. Note that this may be less than the amount you wanted to send. On failure, returns the appropriate error code. This function may return CURLE_AGAIN. In this case, use your operating sys- tem facilities to wait until the socket is writable, and retry. 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_recv(3), curl_easy_setopt(3) libcurl 2026-06-11 curl_easy_send(3)
NAME | SYNOPSIS | DESCRIPTION | PROTOCOLS | EXAMPLE | AVAILABILITY | RETURN VALUE | SEE ALSO
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