Hi,

I am trying to setup a communication between 2 PC say PC1 and PC2 via ethernet using sockets. I've created a simple server program for PC1 and a client program for PC2 and is able to transmit data and echo back to the sender. However, when I swap the order (server program for PC2 and a client program for PC1), I encounter an error saying that "No route to host".
PC1 can ping to PC2 and vice versa, and so I suspect some mechanism is blocking the transmission.

Is there anyone who knows what could be the likely reason?

It may help if we knew what distribution you are using, an idea would be to update the "Distribution" field in your profile.

When you say "No route to host" error, is this an error produced from your program? Do both the server and client give the same error, does it only happen on the client side or server side?

What programming language are you using? What port is the app using? Have you checked firewall settings on either machine?

I am using Red Hat Enterprise Linux WS. I believe the fault is due to the firewire settings. As running the following command:

/etc/rc.d/init.d/iptables stop

will solve my problem and I can run both server/client program on either PC. The problem now is that this is not a permanent solution. As whenever I reboot, the firewalls are activated again. I try deciphering the iptables but some terms looks alien to me.

Can anyone advise me if I still want my firewall to be up, but I also want to allow access of a particular IP say 178.13.18.18 to my pc, how can I do it? And is there a permanent solution that allow a particular IP to access my pc even after rebooting? Please enlighten me. Thanks!




Qn1:What programming language are you using?
I am using C++ with cross complier.

Qn2:What port is the app using?
I randomly select a port greater than 1023.

Hi wiki,
it's obvious that your firewall is blocking your connection. first of all you must issue the command "iptables -F" which will flush your default iptables that was setup when you installed your OS. after that you have to save your changes by issuing the command " service iptables save". this will save the configuration,. after that you have to configure the new rules. you must issue the command
" iptables -I INPUT -d 'your ip' -j REJECT" . then add this command also..
" iptables -I INPUT -d 178.13.18.18 -j ALLOW".
Remember this will block every connection from any systems except 178.13.18.18.
Another very important configuration that i have to suggest is that you dont flush ur default iptables using the command " iptables -F". let it stay.. you just that issue the command " iptables -I INPUT -d 178.13.18.18 -j ALLOW".
now your 178.13.18.18 will be allowed in. after that always remember to save the service using the command " service iptables save" and restart it using " service iptables restart". this must solve your problem .......
please feel free to contact
vimal........

Hi Vimal,

Thanks a lot! Your suggestion work very well.