Perl script for TCP server and client communication. Supports server and client modes via command-line options. Server echoes client input, supports multiple connections, and includes SO_REUSEADDR. Client reads server responses. Features include configurable host/port, non-blocking I/O, and detailed connection logging. Usage: `--mode=server|clie…

tcp_server_client.pl

#!/usr/bin/perl -w
use strict;
use Socket;
use Getopt::Long;
use IO::Handle;

# Configuration
my $default_port = 7890;
my $default_host = 'localhost';
my $backlog = 5;
my $buffer_size = 1024;

# Command-line options
my ($port, $host, $mode, $help);
GetOptions(
    'port=i' => \$port,
    'host=s' => \$host,
    'mode=s' => \$mode,
    'help'   => \$help
) or die "Usage: $0 [--port=<port>] [--host=<host>] [--mode=server|client] [--help]\n";

if ($help) {
    print <<'HELP';
Usage: $0 [options]
Options:
  --port=<port>    Port to use (default: 7890)
  --host=<host>    Host for client mode (default: localhost)
  --mode=<mode>    Mode: 'server' or 'client' (required)
  --help           Show this help message
HELP
    exit 0;
}

$port ||= $default_port;
$host ||= $default_host;
$mode or die "Mode must be specified (--mode=server or --mode=client)\n";
$mode = lc($mode);

# Common socket setup
my $proto = getprotobyname('tcp') or die "Can't get protocol: $!\n";

sub run_client {
    my ($host, $port) = @_;
    
    # Create socket
    socket(my $socket, PF_INET, SOCK_STREAM, $proto)
        or die "Can't create socket: $!\n";
    
    # Connect to server
    my $server_addr = inet_aton($host) or die "Invalid host: $host\n";
    connect($socket, pack_sockaddr_in($port, $server_addr))
        or die "Can't connect to $host:$port: $!\n";
    
    # Set socket to non-blocking
    $socket->autoflush(1);
    
    # Read and print server response
    while (my $line = <$socket>) {
        chomp $line;
        print "Received: $line\n";
    }
    
    close $socket or warn "Client close failed: $!\n";
}

sub run_server {
    my ($port) = @_;
    
    # Create socket
    socket(my $socket, PF_INET, SOCK_STREAM, $proto)
        or die "Can't create socket: $!\n";
    
    # Set socket options
    setsockopt($socket, SOL_SOCKET, SO_REUSEADDR, 1)
        or die "Can't set SO_REUSEADDR: $!\n";
    
    # Bind and listen
    bind($socket, pack_sockaddr_in($port, inet_aton('0.0.0.0')))
        or die "Can't bind to port $port: $!\n";
    listen($socket, $backlog) or die "Listen failed: $!\n";
    
    print "Server started on port $port\n";
    
    # Handle connections
    while (my $client_addr = accept(my $client, $socket)) {
        $client->autoflush(1);
        
        # Get client info
        my ($client_port, $client_ip) = unpack_sockaddr_in($client_addr);
        my $client_host = gethostbyaddr($client_ip, AF_INET) || inet_ntoa($client_ip);
        
        print "Connection from $client_host:$client_port\n";
        
        # Send response
        print $client "Welcome to the server at ", scalar(localtime), "\n";
        
        # Echo client input
        while (my $data = <$client>) {
            chomp $data;
            last if $data eq 'quit';
            print $client "Echo: $data\n";
            print "Received from $client_host: $data\n";
        }
        
        close $client or warn "Client close failed: $!\n";
    }
    
    close $socket or warn "Server close failed: $!\n";
}

# Run in specified mode
if ($mode eq 'client') {
    run_client($host, $port);
} elsif ($mode eq 'server') {
    run_server($port);
} else {
    die "Invalid mode: $mode (use 'server' or 'client')\n";
}