Figure shows a server running both an HTTP server on port 80 and SMTP server running on port 25.  The figure has two clients accessing the server.  Client 1 is sending an HTTP request from source port 49152 to destination port 80.  Client 2 is sending an SMTP request from source port 51152 to destination port 25.  This demonstrates how port numbers are used to differentiate between multiple services running on one server. Figure two highlights the use of the well-known ports for the services. Figure three highlights the use of random source ports as the source ports. Figure four highlights the response from the server to each of the two requests and the fact that the server uses the source port from the request packet as the destination. Figure five highlights the new destination port.