netcat in Ubuntu,
ncat in Fedora, can be used to test a simple tcp(udp) server/client connection.
In a server side, use following command to listen an incoming connection assuming that the port
3300 is used.
netcat -l -p 3300
A client from another machine can make a connection to the server as below assuming that the ip address of server is
netcat 192.168.0.13 3300