curl\_easy\_recv(3) Library Functions Manual curl\_easy\_recv(3)

# [NAME](#NAME)

curl\_easy\_recv - receives raw data on an "easy" connection

# [SYNOPSIS](#SYNOPSIS)

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

# [DESCRIPTION](#DESCRIPTION)

This function receives raw data from the established connection. You may use it together with [*curl\_easy\_send(3)*](/man/os/curl/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 connection setup.

**buffer** is a pointer to your buffer memory that gets populated by the received 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)*](/man/os/curl/CURLOPT_CONNECT_ONLY.3) option before calling [*curl\_easy\_perform(3)*](/man/os/curl/curl_easy_perform.3) or [*curl\_multi\_perform(3)*](/man/os/curl/curl_multi_perform.3). Note that [*curl\_easy\_recv(3)*](/man/os/curl/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)*](/man/os/curl/select.2) to wait for data. The socket may be obtained using [*curl\_easy\_getinfo(3)*](/man/os/curl/curl_easy_getinfo.3) with [*CURLINFO\_ACTIVESOCKET(3)*](/man/os/curl/CURLINFO_ACTIVESOCKET.3).

Wait on the socket only if [*curl\_easy\_recv(3)*](/man/os/curl/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)*](/man/os/curl/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)*](/man/os/curl/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](#PROTOCOLS)

This functionality affects all supported protocols

# [EXAMPLE](#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](#AVAILABILITY)

Added in curl 7.18.2

# [RETURN VALUE](#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 system 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](#SEE_ALSO)

[**curl\_easy\_getinfo**(3)](/man/os/curl/curl_easy_getinfo.3), [**curl\_easy\_perform**(3)](/man/os/curl/curl_easy_perform.3), [**curl\_easy\_send**(3)](/man/os/curl/curl_easy_send.3), [**curl\_easy\_setopt**(3)](/man/os/curl/curl_easy_setopt.3)

2026-10-01 libcurl

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Document: curl_easy_recv(3) from curl 8.22.0-r4 (Chainguard OS)
Source: https://github.com/curl/curl.git