PHP socket_set_blocking Function

last modified April 4, 2025

The PHP socket_set_blocking function controls the blocking mode of a socket. It determines whether socket operations will wait for completion.

Basic Definition

socket_set_blocking sets a socket to blocking or non-blocking mode. In blocking mode, operations wait until they can complete.

Syntax: socket_set_blocking(Socket $socket, bool $enable): bool. Returns true on success, false on failure. Affects all subsequent operations.

Basic Blocking Socket Example

This example demonstrates creating a blocking socket for a simple TCP client.

blocking_socket.php

<?php

declare(strict_types=1);

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); if ($socket === false) { die(“Socket creation failed”); }

// Set socket to blocking mode socket_set_blocking($socket, true);

$connected = socket_connect($socket, ’example.com’, 80); if ($connected === false) { die(“Connection failed”); }

echo “Connected in blocking mode\n”; socket_close($socket);

This creates a TCP socket in blocking mode. The connect operation will wait until it succeeds or fails. Blocking mode is simpler for basic operations.

Non-blocking Socket Example

This shows how to create a non-blocking socket for asynchronous operations.

non_blocking_socket.php

<?php

declare(strict_types=1);

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); if ($socket === false) { die(“Socket creation failed”); }

// Set socket to non-blocking mode socket_set_blocking($socket, false);

$connected = socket_connect($socket, ’example.com’, 80); if ($connected === false) { $error = socket_last_error($socket); if ($error !== SOCKET_EINPROGRESS) { die(“Connection failed”); } echo “Connection in progress\n”; }

socket_close($socket);

Non-blocking mode returns immediately. The code must handle EINPROGRESS errors. This allows for asynchronous network programming.

Switching Between Modes

This example demonstrates dynamically switching between blocking modes.

mode_switching.php

<?php

declare(strict_types=1);

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); socket_connect($socket, ’example.com’, 80);

// Start in blocking mode for initial data socket_set_blocking($socket, true); $data = socket_read($socket, 1024);

// Switch to non-blocking for subsequent reads socket_set_blocking($socket, false);

while (true) { $more = socket_read($socket, 1024); if ($more === false) break; $data .= $more; }

echo “Received data: " . strlen($data) . " bytes\n”; socket_close($socket);

This starts in blocking mode for initial data, then switches to non-blocking. The approach combines both modes for flexible network communication.

Timeout Handling with Blocking Sockets

This example shows how to implement timeouts with blocking sockets.

timeout_handling.php

<?php

declare(strict_types=1);

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); socket_set_blocking($socket, true);

// Set timeout options socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, [ “sec” => 5, “usec” => 0 ]);

$connected = socket_connect($socket, ’example.com’, 80); if ($connected === false) { die(“Connection failed”); }

$data = socket_read($socket, 1024); if ($data === false) { die(“Read timed out after 5 seconds”); }

echo “Received data: $data\n”; socket_close($socket);

Even in blocking mode, timeouts can be set using socket options. This prevents indefinite waits while maintaining blocking simplicity.

Non-blocking Socket Server

This example creates a simple non-blocking socket server.

non_blocking_server.php

<?php

declare(strict_types=1);

$server = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); socket_bind($server, ‘0.0.0.0’, 8080); socket_listen($server);

// Set server socket to non-blocking socket_set_blocking($server, false);

echo “Server running on port 8080 (non-blocking)\n”;

while (true) { $client = socket_accept($server); if ($client === false) { usleep(100000); // Sleep to prevent CPU overload continue; }

$data = "HTTP/1.1 200 OK\r\nContent-Length: 13\r\n\r\nHello, World!";
socket_write($client, $data);
socket_close($client);

}

The non-blocking server checks for connections without waiting. It sleeps briefly when no connections are available to reduce CPU usage.

Best Practices

• Error Handling: Always check socket operation return values

• Resource Management: Close sockets properly when done

• Performance: Use non-blocking for high-concurrency servers

• Simplicity: Prefer blocking mode for simple clients

• Timeouts: Set appropriate timeouts for blocking operations

Source

PHP socket_set_blocking Documentation

This tutorial covered the PHP socket_set_blocking function with practical examples for different network programming 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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