How to set up ntalk server on OS X?

Question

I'm trying to set up ntalk on os x yosemite.

I run:

$ sudo launchctl load -w /System/Library/LaunchDaemons/ntalk.plist

But port 518 is still closed…

$ sudo nmap -sS -p 518 localhost
Password:

Starting Nmap 6.47 ( http://nmap.org ) at 2015-09-07 12:09 PDT
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000099s latency).
PORT    STATE  SERVICE
518/tcp closed ntalk

Nmap done: 1 IP address (1 host up) scanned in 0.05 seconds

What's the problem?

Answer 1

If you look into the /System/Library/LaunchDaemons/ntalk.plist then you can see the following entry:

<dict>
    <key>Listeners</key>
    <dict>
        <key>SockServiceName</key>
        <string>ntalk</string>
        <key>SockType</key>
        <string>dgram</string>
    </dict>
</dict>

The value of SockType is dgram and because of that the program listens on a UDP and not a TCP port.

If you call sudo nmap -sU -p 518 localhost then you should see that the port is opened.

vanemery.com: Using ntalkd as a Private, Secure, One-on-One Text Chat Service:

ntalkd listens on UDP port 518. Once the actual session is setup, there are two UDP streams and one TCP connection that exist between clients.