tcpmon is an open-source utility for monitoring the data flowing on a TCP connection. tcpmon is used by placing it in-between a client and a server. The client is made to connect to tcpmon, and tcpmon forwards the data to server along-with displaying it in its GUI.

Download: Two ways to launch tcpmon

1. Click here to run the latest version of tcpmon directly from Web. If a security warning dialog appears, click on the "Yes" button to grant tcpmon permissions to run.
2. Download tcpmon and simply double-click on the downloaded executable jar file to launch tcpmon.

Using tcpmon

The client will connect to the Local Port on the host where tcpmon is running. The address of the server should be specified in Server Name and Server Port. Information captured for each connection is displayed in a tabbed panel identified by the local port of the connection.

Note that the client needs to connect to the machine where tcpmon is running on the "Local Port", not directly to the server.

See the sites page for tcpmon.