curl_easy_recv - Online Linux Manual Page

Section : 3
Updated : November 26, 2021
Source : libcurl 7.82.0
Note : libcurl Manual

NAME

curl_easy_recv - receives raw data on an "easy" connection

SYNOPSIS

#include <curl/easy.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 will take care of proxy negotiation and connection set-up.

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

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)

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.

EXAMPLE

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); }

AVAILABILITY

Added in 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

. 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