The moment of truth: connect the computers with the null modem cable, first start the server side (if you are using the "/etc/inittab" approach it should be up already), then start the client side. You should see something like this on the server:
[root@griis /root]# pppd /dev/ttyS1 nodetach Using interface ppp0 Connect: ppp0 <--> /dev/ttyS1 user zaphod logged in Deflate (15) compression enabled local IP address 192.168.0.1 remote IP address 192.168.1.1
Note that if you started pppd from the "/etc/inittab" file these messages will appear in "/var/log/messages". On the client side you should see something like this:
[root@wylg /root]# pppd /dev/ttyS0 nodetach Using interface ppp0 Connect: ppp0 <--> /dev/ttyS0 Remote message: Success Deflate (15) compression enabled local IP address 192.168.1.1 remote IP address 192.168.0.1
On either side you can ping the other computer to see if the connection is active:
[zaphod@wylg zaphod]$ ping 192.168.0.1 PING 192.168.0.1 (192.168.0.1) from 192.168.1.1 : 56(84) bytes of data. 64 bytes from 192.168.0.1: icmp_seq=0 ttl=255 time=31.7 ms 64 bytes from 192.168.0.1: icmp_seq=1 ttl=255 time=20.3 ms 64 bytes from 192.168.0.1: icmp_seq=2 ttl=255 time=19.2 ms 64 bytes from 192.168.0.1: icmp_seq=3 ttl=255 time=20.3 ms --- 192.168.0.1 ping statistics --- 4 packets transmitted, 4 packets received, 0% packet loss round-trip min/avg/max = 19.2/22.8/31.7 ms
You can now access the server through any TCP/IP services it might have available, such as FTP, HTTP, TELNET and SAMBA.