CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UNIX_SOCKET_PATH, char *path);
When enabled, curl will connect to the Unix domain socket instead of establishing a TCP connection to a host. Since no TCP connection is created, curl does not need to resolve the DNS hostname in the URL.
The maximum path length on Cygwin, Linux and Solaris is 107. On other platforms it might be even less.
Proxy and TCP options such as CURLOPT_TCP_NODELAY(3) are not supported. Proxy options such as CURLOPT_PROXY(3) have no effect either as these are TCP-oriented, and asking a proxy server to connect to a certain Unix domain socket is not possible.
The application does not have to keep the string around after setting this option.
curl_easy_setopt(curl_handle, CURLOPT_UNIX_SOCKET_PATH, "/tmp/nginx.sock"); curl_easy_setopt(curl_handle, CURLOPT_URL, "http://localhost/");
If you are on Linux and somehow have a need for paths larger than 107 bytes, you could use the proc filesystem to bypass the limitation:
int dirfd = open(long_directory_path_to_socket, O_DIRECTORY | O_RDONLY); char path[108]; snprintf(path, sizeof(path), "/proc/self/fd/%d/nginx.sock", dirfd); curl_easy_setopt(curl_handle, CURLOPT_UNIX_SOCKET_PATH, path); /* Be sure to keep dirfd valid until you discard the handle */