port number 1

[Rodolph]

Hello,
Someone could explained me what is the port number 1 ? what does it do ? If i can use it ?
thanks

[Deepak Extross]

Port 1 is usually for TCP Port multiplexer.
In case you're looking for a port to use for a service of your own, avoid the "well-known" ports (0 thru' 1023).

[U.SivaKumar_2 · Accepted solution]

Hi,
TCP Port Service Multiplexer. TCPMUX listens on port 1. When a connection is established, it is supposed to send the name of the service it wants to connect, and the selected protocol starts if available. TCPMUX is defined in RFC 1078 at http://www.ietf.org/rfc/rfc1078.txt, but never gained any popularity and is considered deprecated.

It is considered as a security threat as scans
and exploit based attacks can be launched on this port.

regards,
U.SivaKumar

[Paula J Frazer-Campbell]

Hi

Have a look in /etc/services:-

tcpmux 1/tcp # TCP port multiplexer (RFC 1078)
echo 7/tcp # Echo
echo 7/udp #
discard 9/tcp sink null # Discard
discard 9/udp sink null #
systat 11/tcp users # Active Users
daytime 13/tcp # Daytime
daytime 13/udp #
qotd 17/tcp quote # Quote of the Day



ETC -


Paula

[Rodolph]

to Mr U.Sivacumar,

Can you give me more details please ? In fact, I want to use this port in oder to check if my server is up and running ,by opening a socket and check the inetd. Is a good solution ?

[Paula J Frazer-Campbell]

Hi
Do not use port 1 fot this,
in /etc/services add a port say 5007.

A ping to a server will only indicate that the network card is up.


An easier way is to get the server to send a "heartbeat" to another server ( ftp a file) and the on the monitoring server check the file for tate and time stamp.

The fact that the monitored server can carry out an ftp is far better than relying on a ping.


Paula

Paula

[Andrew Cowan]

If you use ports higher than 1024 they don't need root access, which is also better for security.

If you just want to see if the server is alive use SNMPINFO and examine variable such as SYSDESCR. This is how products such as Openview work.

[Bill Thorsteinson]

There are various monitor scripts available that will
check to see if a service is responding from a host.
Some will page if one of several services go down.

Look for packages like Big Brother or Mon.

You can also use tools like ssh to see if a computer is
aloive. Script a loop around a command like:

ssh unprivuser@requiredhost ls > /dev/null 2>&1

and check the return code.