314. Briefly: Installing talkd on ROCKS 5.4.3

I was asked to set up talkd on our Rocks 5.4.3 cluster (Centos 5.4) . There's no talkd or talk-server packages in the repos on that server.

Note: The general consensus seems to be that talk is
1. insecure and
2. outdated.

To install:

wget http://mirror.centos.org/centos/5/os/x86_64/CentOS/talk-server-0.17-31.el5.x86_64.rpm
yum localinstall talk-server-0.17-31.el5.x86_64.rpm
sudo iptables -A INPUT -p udp --dport 517 -s 127.0.0.1 -j ACCEPT
sudo iptables -A INPUT -p udp --dport 518 -s 127.0.0.1 -j ACCEPT

Above I've added, but haven't yet tried, -s 127.0.0.1 to limit connections from the local computer (localhost). If it doesn't work with -s 127.0.0.1, then try without -- but then be aware of the security implications. These rules also aren't permanent and will be lost on reboot. To make them permanent, edit /etc/sysconfig/iptables.

I couldn't get talk to work before opening the ports and would get

Error on read from talk daemon : Connection refused

Note that talkd uses Xinet and not init -- it will not run as  memory resident daemon, but instead be launched by xinet only when talkd is needed (traffic is detected to the ports associated with talkd). Xinet.d is a bit like a concierge, waking up whomever seems to be the adressee.

Edit both /etc/xinetd.d/talk and /etc/xinetd.d/ntalk. Change to:

# default: off
# description: The talk server accepts talk requests for chatting with users \
#       on other systems.
service talk
{
        flags                   = IPv4
        disable                 = no
        socket_type             = dgram
        wait                    = yes
        user                    = nobody
        group                   = tty
        server                  = /usr/sbin/in.talkd
}

Finally, restart xinet.d (doing chkconfig talk on wasn't enough):

sudo /etc/init.d/xinet.d restart

---

Note: If you or the other user have several terminals open you should figure out which terminal to use. If you're user2, do

ps

PID TTY          TIME CMD
 5455 pts/23   00:00:00 bash
 9321 pts/23   00:00:00 ps

user1 can then do

[user1@host ~]$ talk user2@localhost pts/23

and user2 will see the following in that terminal:

Message from Talk_Daemon@host at 14:49 ...   
talk: connection requested by user1@localhost.localdomain.  
talk: respond with:  talk user1@localhost.localdomain 

If you are user1 and have no idea on what terminal user2 is logged on, you can try

w|grep user2

user2     pts/8    remote:S.0    04Nov12 59:00   0.04s  0.04s /bin/bash
user2     pts/9    remote:S.1    04Nov12 17:28   0.03s  0.03s /bin/bash
user2     pts/10   remote Mon12  2days  0.03s  0.00s ssh -X -v volde
user2     pts/11   local  Mon12  2days  0.29s  0.26s perl eccejobmon
user2     pts/23   remote 14:30  7.00s  0.00s  0.00s -bash