The Real-Time Echo Server example (rt_echo_server.o) opens and connects a socket to UDP port 7. Every packet that is received on this port is duplicated and returned to the source. It is very similar to the ICMP ping service, but it uses a different protocol. The server is activated by loading the rt_echo_server.o module, and deactivated by removing the module. No output is sent to the console, except in the case of an error.
UDP echo service is a standard network service that is useful for testing, but is usually disabled by default. A non-real-time server for normal networking can be enabled in the inetd server by editing /etc/services.
The Real-Time Echo Client example (rt_echo_client.o) starts a real-time task that periodically sends packets to UDP port 7 of an echo server. When a reply is received, it prints a message to the console. The message includes the time it takes to send and receive the packet, which is expressed in TSC cycles.
For your convenience, an implementation of a non-real-time echo client has been provided.