opening port 7 (echo port) on Linux/Debian

Question

I need an echo server on my Linux/Debian for debugging purposes , I realized that there is an assigned port shown in '/etc/services' to do that already and it's port 7 TCP/UDP.

Is it possible to open this port on Linux (Debian)? if not, what are alternatives?

Solution

For setting up a echo service in Debian, you can install xinetd with:

apt-get install xinetd

Than you have to change the disable directive to no in /etc/xinetd.d/echo; or if the file does not exist, create it as shown here:

# default: off
# description: An xinetd internal service which echo's characters back to
# clients.
# This is the tcp version.
service echo
{
    disable     = no
    type        = INTERNAL
    id      = echo-stream
    socket_type = stream
    protocol    = tcp
    user        = root
    wait        = no
}

# This is the udp version.
service echo
{
    disable     = yes
    type        = INTERNAL
    id      = echo-dgram
    socket_type = dgram
    protocol    = udp
    user        = root
    wait        = yes
}

After setting disable = no, or creating the file, your restart xinetd with:

sudo service xinetd restart

To test the echo TCP service:

$nc localhost echo
testing...
testing...
xxxx
xxxx
^C

Comments

[Stephen Kitt]

Not quite a duplicate, but the linked question contains the answer to this one.

[Rui F Ribeiro]

Why the echo service?

[Brian Salehi]

@StephenKitt unfortunately there is no 'inetd.conf' file in '/etc', I guess this file can be found in RH not Debian. there should be a new method to enable this service

[Brian Salehi]

@RuiFRibeiro just learning Linux network programming,simplest client codes can send a string to an echo server and receive it. there should be an echo server to test the client.

[Stephen Kitt]

@Rui I wouldn’t any more, but each to his own :-).

[Brian Salehi]

@RuiFRibeiro now I remember xinetd I worked with it years ago! helped a lot thanks

[Rui F Ribeiro]

I added an answer.

[Stephen Kitt]

It’s not a good idea to enable UDP echo...

[Rui F Ribeiro]

@StephenKitt Indeed, it was as an example, however from a security point of view is generally a bad ideia. Edited the answer.