Open Internet or Unix domain socket connection

Description

stream_socket_client(
    string $address,
    int &$error_code = null,
    string &$error_message = null,
    ?float $timeout = null,
    int $flags = STREAM_CLIENT_CONNECT,
    ?resource $context = null
): resource|false

Initiates a stream or datagram connection to the destination specified by address. 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 address 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.

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

Parameters

address

Address to the socket to connect to.

error_code

Will be set to the system level error number if connection fails.

error_message

Will be set to the system level error message if the connection fails.

timeout

Number of seconds until the connect() system call should timeout. By default, default_socket_timeout is used.

Note: This parameter only applies when not making asynchronous connection attempts.

Note:
To set a timeout for reading/writing data over the socket, use the stream_set_timeout(), as the timeout only applies while making connecting the socket.

flags

Bitmask field which may be set to any combination of connection flags. Currently the select of connection flags is limited to STREAM_CLIENT_CONNECT (default), STREAM_CLIENT_ASYNC_CONNECT and STREAM_CLIENT_PERSISTENT.

context

A valid context resource created with stream_context_create().

Return Values

On success a stream resource is returned which may be used together with the other file functions (such as fgets(), fgetss(), fwrite(), fclose(), and feof()), false on failure.

Errors/Exceptions

On failure the error_code and error_message arguments will be populated with the actual system level error that occurred in the system-level connect() call. If the value returned in error_code 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 error_code and error_message arguments will always be passed by reference.

Changelog

Version	Description
8.0.0	`timeout` and `context` are now nullable.

Examples

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);
}
?>

Example #2 Using UDP connection

Retrieving the day and time from the UDP service "daytime" (port 13) on localhost.


<?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);
}
?>

Notes

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.

Note:
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 List of Supported Socket Transports for a list of built in transports.

stream_socket_client