Problems with network connections can be hard to diagnose as one can appear connected even when the IP address is invalid for DHCP connectivity, such as an APIPA. Sentinel is a handy portable application for Network Administrators which tests your TCP communication to help determine if your computer is online. It uses the TCP (Transmission Control Protocol) to send data message unit to help you check if the message is successfully sent.
Just enter an IP address (e.g. of a DHCP server) and click Connect to connect to a host or specify a server port and click Start. Once done, you will be able to send a test message for checking your TCP connection.
If your computer is properly connected to the network, a new window will pop-up informing you that the test message was sent successfully.
aSentinel is an open source application which works on