Can telnet port 80 but cannot ping!

[jc at trillian.mit.edu (John Chambers)]

| I am running RedHat Linux 7.2 on a Compaq DeskPro.
| I can successfully:
| 	telnet <My-Host> 80

This  shows  that  you  have  a  web  server  running  and  accepting
connections. One question: Did you do this from your machine, or from
a machine outside your ISP? Lots of ISPs block port 80.  When they do
this, you will be able to use your web server from home, but not from
the outside.  This can be really annoying when you are  at  work  and
want  to  fetch something from home.  But most ISPs don't give a damn
about geeks trying to do such  things;  they  only  care  about  fast
browser access from your machine to commercial web sites.

| However, if I try:
| 	telnet <My-Host>
| it responds:
| 	"telnet: Unable to connect to ...."

This shows that you don't have a telnet server (daemon) running.   It
would  be on port 23, the default telnet port.  The ps command should
show a telnetd process running. If it's there (and netstat -a shows a
listener  on  port 23), then the problem is probably that your ISP is
blocking port 23.

| I have also tried:
| 	ping <My-Host>
| but it says:
| 	"no answer from h00045adc236a.ne.mediaone.net"

Most likely this means that mediaone.net is  blocking  ICMP  traffic.
It's  pretty common for commercial gateways and firewalls to do this,
though it's really annoying to  anyone  trying  to  diagnose  network
problems.

| Any idea what steps I should take to make these services available
| on my server? I should mention that I chose the telnet and other
| modules during my installation of of my Linux.

Installing telnet isn't necessarily the same as installing  a  telnet
server.  You can always use the "telnet" command to connect from your
machine to another.  But if you want to connect  *to*  your  machine,
you'd need telnetd running.

One warning:  There is a strong anti-telnetd movement growing in  the
unix  world,  due  to the fact that telnet sends passwords across the
network in the clear.  Anyone with a traffic monitor  can  find  your
login id and password, if your packets go through their machine.  I'd
recommend getting OpenSSH, and installing  it.   You  want  both  the
client  and  server (sshd) on your home machine, and an ssh client on
any machine you want to connect  from.   I've  done  this  on  a  few
machines.  Go to openssh.org and grab the latest release. It's pretty
easy, and then nobody will be able to intercept your passwords.

(The telnet command itself isn't a problem.  It's a useful  tool  for
such jobs as connecting to a web server as a sanity check.  It's only
a problem when the connection requires passwords.)