PHP: fsockopen

Description

fsockopen(
    string $hostname,
    int $port = -1,
    int &$error_code = null,
    string &$error_message = null,
    ?float $timeout = null
): resource|false

Initiates a socket connection to the resource specified by hostname.

PHP supports targets in the Internet and Unix domains as described in List of Supported Socket Transports. A list of supported transports can also be retrieved using stream_get_transports().

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

The function stream_socket_client() is similar but provides a richer set of options, including non-blocking connection and the ability to provide a stream context.

Parameters

hostname

If OpenSSL support is installed, you may prefix the hostname with either ssl:// or tls:// to use an SSL or TLS client connection over TCP/IP to connect to the remote host.

port

The port number. This can be omitted and skipped with -1 for transports that do not use ports, such as unix://.

error_code

If provided, holds the system level error number 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.

error_message

The error message as a string.

timeout

The connection timeout, in seconds. When null, the default_socket_timeout php.ini setting is used.

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

Return Values

fsockopen() returns a file pointer 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

Errors/Exceptions

Throws E_WARNING if hostname is not a valid domain.

Changelog

Version	Description
8.0.0	`timeout` is nullable now.

Examples

Example #1 fsockopen() Example

<?php
$fp = fsockopen("www.example.com", 80, $errno, $errstr, 30);
if (!$fp) {
    echo "$errstr ($errno)<br />\n";
} else {
    $out = "GET / HTTP/1.1\r\n";
    $out .= "Host: www.example.com\r\n";
    $out .= "Connection: Close\r\n\r\n";
    fwrite($fp, $out);
    while (!feof($fp)) {
        echo fgets($fp, 128);
    }
    fclose($fp);
}
?>

Example #2 Using UDP connection

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

<?php
$fp = fsockopen("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

Note:
Depending on the environment, the Unix domain or the optional connect timeout may not be available.

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.

fsockopen