PHP Manual: stream_socket

Description

resource stream_socket_client ( string remote_socket [, int &errno [, string &errstr [, float timeout [, int flags [, resource context]]]]] )

Initiates a stream or datagram connection to the destination specified by remote_socket. The type of socket created is determined by the transport specified using standard URL formatting: transport://target. For Internet Domain sockets (AF_INET) such as TCP and UDP, the target portion of the remote_socket parameter should consist of a hostname or IP address followed by a colon and a port number. For Unix domain sockets, the target portion should point to the socket file on the filesystem. The optional timeout can be used to set a timeout in seconds for the connect system call. flags is a bitmask field which may be set to any combination of connection flags. Currently the selection of connection flags is limited to STREAM_CLIENT_CONNECT (default), STREAM_CLIENT_ASYNC_CONNECT and STREAM_CLIENT_PERSISTENT.

Note: If you need to set a timeout for reading/writing data over the socket, use stream_set_timeout(), as the timeout parameter to stream_socket_client() only applies while connecting the socket.

stream_socket_client() returns a stream resource which may be used together with the other file functions (such as fgets(), fgetss(), fwrite(), fclose(), and feof()).

If the call fails, it will return FALSE and if the optional errno and errstr arguments are present they will be set to indicate the actual system level error that occurred in the system-level connect() call. If the value returned in errno is 0 and the function returned FALSE, it is an indication that the error occurred before the connect() call. This is most likely due to a problem initializing the socket. Note that the errno and errstr arguments will always be passed by reference.

Depending on the environment, the Unix domain or the optional connect timeout may not be available. A list of available transports can be retrieved using stream_get_transports(). See Appendix O for a list of built in transports.

The stream will by default be opened in blocking mode. You can switch it to non-blocking mode by using stream_set_blocking().

Example 1. stream_socket_client() Example

<?php
$fp = stream_socket_client("tcp://www.example.com:80", $errno, $errstr, 30);
if (!$fp) {
    echo "$errstr ($errno)<br />\n";
} else {
    fwrite($fp, "GET / HTTP/1.0\r\nHost: www.example.com\r\nAccept: */*\r\n\r\n");
    while (!feof($fp)) {
        echo fgets($fp, 1024);
    }
    fclose($fp);
}
?>

The example below shows how to retrieve the day and time from the UDP service "daytime" (port 13) in your own machine.

Example 2. Using UDP connection

<?php
$fp = stream_socket_client("udp://127.0.0.1:13", $errno, $errstr);
if (!$fp) {
    echo "ERROR: $errno - $errstr<br />\n";
} else {
    fwrite($fp, "\n");
    echo fread($fp, 26);
    fclose($fp);
}
?>

Warning

UDP sockets will sometimes appear to have opened without an error, even if the remote host is unreachable. The error will only become apparent when you read or write data to/from the socket. The reason for this is because UDP is a "connectionless" protocol, which means that the operating system does not try to establish a link for the socket until it actually needs to send or receive data.

Note: When specifying a numerical IPv6 address (e.g. fe80::1) you must enclose the IP in square brackets. For example, tcp://[fe80::1]:80.