When working with legacy HP-UX systems in production environments, verifying UDP connectivity to remote servers presents unique challenges. Unlike TCP where telnet provides a quick test, UDP requires different approaches since it's connectionless by design.

HP-UX includes several built-in tools that can help without requiring additional installations:

# Using rpcinfo (if RPC services are running)
rpcinfo -u remote_host port_number

# Using snoop (HP-UX packet sniffer)
snoop -o /tmp/udptest.pcap port port_number and host remote_host

For a simple test, you can use the scripting approach with /dev/udp:

# Basic UDP test script
(
  exec 3>/dev/udp/remote_host/port_number
  echo "test" >&3
  exec 3>&-
) & sleep 1; kill $!

When native tools aren't sufficient, consider these production-safe methods:

• Create a small UDP listener on a test machine you control
• Use scripting to generate UDP packets
• Check firewall logs for blocked traffic

Example UDP sender in Perl:

#!/usr/bin/perl
use IO::Socket::INET;
my $sock = IO::Socket::INET->new(
    PeerAddr => 'remote_host',
    PeerPort => port_number,
    Proto    => 'udp'
) or die "Cannot create socket: $!";
print $sock "UDP test";
close($sock);

Since UDP provides no confirmation, successful transmission doesn't guarantee the remote end received it. Look for:

• No immediate errors from your commands
• Network monitoring showing outbound packets
• Response packets if the remote service replies

Verifying UDP connectivity from HP-UX systems presents unique challenges compared to TCP testing. Unlike TCP's connection-oriented protocol where tools like telnet work, UDP requires different approaches since it's connectionless. Production HP-UX environments often lack modern networking tools, making this verification trickier.

Fortunately, HP-UX includes several built-in utilities that can help:

# Using rpcinfo (if RPC services are running)
rpcinfo -u remote_host port_number

# Using lsof to check if local UDP ports are open
lsof -i UDP:port_number

# Basic UDP test with system logger
logger -p local0.debug "Test message" | socat - udp:remote_host:port

When standard tools aren't available, consider these approaches:

# Using Perl one-liner
perl -e 'use Socket; socket(S, PF_INET, SOCK_DGRAM, getprotobyname("udp")); 
$remote = sockaddr_in(port_number, inet_aton("remote_host")); 
send(S, "test", 0, $remote) or die "Cannot send: $!";'

# Simple shell script with /dev/udp (if supported)
echo "test" > /dev/udp/remote_host/port_number

Since UDP doesn't guarantee delivery, you'll need indirect verification methods:

• Check firewall logs on the remote host
• Use packet capture tools on intermediate systems
• Monitor network traffic with HP-UX's nettl

When working with production HP-UX systems:

• Always test during maintenance windows
• Use the least intrusive methods first
• Document all commands before execution
• Have rollback procedures ready