PHP getprotobyname Function
last modified April 4, 2025
The PHP getprotobyname function converts protocol names to their
corresponding protocol numbers. It's useful in network programming.
Basic Definition
getprotobyname looks up protocol names in the system's protocol
database. It returns the protocol number associated with the given name.
Syntax: getprotobyname(string $name): int|false. Returns the
protocol number or false if not found. Requires proper system configuration.
Basic Protocol Lookup
This example demonstrates converting common protocol names to their numbers.
<?php
declare(strict_types=1);
$protocol = "tcp";
$number = getprotobyname($protocol);
if ($number !== false) {
echo "Protocol $protocol has number $number";
} else {
echo "Protocol $protocol not found";
}
This checks the system's protocol database for the TCP protocol number. TCP is commonly used for reliable network communication.
Checking Multiple Protocols
This example checks multiple protocol names and displays their numbers.
<?php
declare(strict_types=1);
$protocols = ["tcp", "udp", "icmp", "ip"];
foreach ($protocols as $proto) {
$num = getprotobyname($proto);
echo "$proto: " . ($num !== false ? $num : "Not found") . "\n";
}
This provides a quick reference for common protocol numbers. Different protocols serve different purposes in network communication.
Error Handling
This example shows proper error handling when a protocol isn't found.
<?php
declare(strict_types=1);
$protocol = "nonexistent";
$number = getprotobyname($protocol);
if ($number === false) {
throw new RuntimeException("Protocol $protocol not found in database");
}
echo "Protocol number: $number";
Always check for false return values when the protocol might not exist. This prevents undefined behavior in network applications.
Socket Creation Example
This demonstrates using getprotobyname in socket creation.
<?php
declare(strict_types=1);
$protocol = "tcp";
$proto_num = getprotobyname($protocol);
if ($proto_num === false) {
die("Cannot get protocol number for $protocol");
}
$socket = socket_create(AF_INET, SOCK_STREAM, $proto_num);
if ($socket === false) {
die("Socket creation failed: " . socket_strerror(socket_last_error()));
}
echo "TCP socket created successfully";
This shows practical use in network programming where protocol numbers are required for socket operations.
Protocol Validation Function
This creates a reusable function to validate protocol names.
<?php
declare(strict_types=1);
function validateProtocol(string $name): bool {
return getprotobyname($name) !== false;
}
$test_protocols = ["udp", "icmp", "fake_proto"];
foreach ($test_protocols as $proto) {
$status = validateProtocol($proto) ? "valid" : "invalid";
echo "$proto is $status\n";
}
This function provides a clean way to check if a protocol name exists in the system database before using it.
Best Practices
- Caching: Cache results to avoid repeated lookups
- Error Handling: Always check for false returns
- Case Sensitivity: Protocol names are case-sensitive
- Portability: Protocol numbers may vary between systems
Source
PHP getprotobyname Documentation
This tutorial covered the PHP getprotobyname function with practical
examples for protocol name to number conversion in network programming.