PHP: fsockopen

If you are new to PHP or just need to refresh your skills, this is the place to start. This series of tutorials will give you the basic knowledge you will need to create a simple PHP website.

PHP is a reflective programming language originally designed for producing dynamic web pages.[1] PHP is used mainly in server-side scripting, but can be used from a command line interface or in standalone graphical applications. Textual User Interfaces can also be created using ncurses.

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fsockopen

Description

resource fsockopen ( string target [, int port [, int &errno [, string &errstr [, float timeout]]]] )

Initiates a socket connection to the resource specified by target. PHP supports targets in the Internet and Unix domains as described in Appendix P. A list of supported transports can also be retrieved using stream_get_transports().

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.

As of PHP 4.3.0, if you have compiled in OpenSSL support, 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.

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 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.

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

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);
}
?>

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 = 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);
}
?>

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: The timeout parameter was introduced in PHP 3.0.9 and UDP support was added in PHP 4.

See also pfsockopen(), stream_set_blocking(), stream_set_timeout(), fgets(), fgetss(), fwrite(), fclose(), feof(), and the Curl extension.

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fsockopen

Description