PHP fsockopen Function

last modified April 4, 2025

The PHP fsockopen function opens a network socket connection. It enables low-level network communication with various protocols.

Basic Definition

fsockopen initiates a socket connection to a specified host. It works with TCP/IP sockets for both IPv4 and IPv6 addresses.

Syntax: fsockopen(string $hostname, int $port, int &$errno, string &$errstr, float $timeout = ini_get(“default_socket_timeout”)): resource|false. Returns a file pointer on success, false on failure.

Basic HTTP Request

This example demonstrates making a simple HTTP GET request using fsockopen.

http_request.php

<?php

declare(strict_types=1);

$fp = fsockopen(“www.example.com”, 80, $errno, $errstr, 30);

if (!$fp) { echo “Error: $errstr ($errno)”; } 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);

}

This connects to example.com on port 80 (HTTP), sends a GET request, and reads the response. The connection is properly closed afterward.

SMTP Email Sending

This shows how to send an email through SMTP using raw socket communication.

smtp_email.php

<?php

declare(strict_types=1);

$smtp = fsockopen(“smtp.example.com”, 25, $errno, $errstr, 30);

if (!$smtp) { die(“Error: $errstr ($errno)”); }

$commands = [ “EHLO localhost\r\n”, “MAIL FROM: <sender@example.com>\r\n”, “RCPT TO: <recipient@example.com>\r\n”, “DATA\r\n”, “Subject: Test\r\n\r\nHello World\r\n.\r\n”, “QUIT\r\n” ];

foreach ($commands as $cmd) { fwrite($smtp, $cmd); echo fgets($smtp, 256); }

fclose($smtp);

This connects to an SMTP server and sends a basic email by issuing SMTP commands directly. Each command receives a response from the server.

Port Scanner

This example creates a simple port scanner to check open ports on a host.

port_scanner.php

<?php

declare(strict_types=1);

function scanPort($host, $port, $timeout = 1) { $fp = @fsockopen($host, $port, $errno, $errstr, $timeout); if ($fp) { fclose($fp); return true; } return false; }

$host = “example.com”; $ports = [21, 22, 25, 80, 443];

foreach ($ports as $port) { $status = scanPort($host, $port) ? “open” : “closed”; echo “Port $port is $status\n”; }

The function attempts to connect to each port with a short timeout. If connection succeeds, the port is open. This is a basic security tool.

Custom TCP Client

This demonstrates a custom TCP client that sends and receives data.

tcp_client.php

<?php

declare(strict_types=1);

$socket = fsockopen(“tcp://127.0.0.1”, 9000, $errno, $errstr, 30);

if (!$socket) { die(“Error: $errstr ($errno)”); }

fwrite($socket, “Hello Server!\n”); echo “Server says: " . fgets($socket, 1024);

fclose($socket);

This connects to a local TCP server on port 9000, sends a message, and reads the response. Useful for custom protocol implementations.

HTTPS Connection

This shows how to establish a secure HTTPS connection using fsockopen.

https_request.php

<?php

declare(strict_types=1);

$host = “www.example.com”; $port = 443; $timeout = 30;

$fp = fsockopen(“ssl://$host”, $port, $errno, $errstr, $timeout);

if (!$fp) { die(“Error: $errstr ($errno)”); }

$out = “GET / HTTP/1.1\r\n”; $out .= “Host: $host\r\n”; $out .= “Connection: Close\r\n\r\n”;

fwrite($fp, $out); while (!feof($fp)) { echo fgets($fp, 128); } fclose($fp);

This connects to port 443 (HTTPS) using the ssl:// protocol prefix. The rest works like HTTP but with encrypted transport layer security.

Best Practices

• Error Handling: Always check for connection errors

• Timeouts: Set appropriate timeout values

• Resource Cleanup: Always close connections with fclose

• Security: Validate all input to prevent injection

• Performance: Reuse connections when possible

Source

PHP fsockopen Documentation

This tutorial covered the PHP fsockopen function with practical examples for various network communication scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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