Hello,

My colleague and I are troubleshooting an issue that has us scratching our heads. Here is how our system is setup.

Our host application is configured as a TCP server listening on port 1001.

The Client device is configured as a TCP client configured to connect to the host application on port 1001. Once the device makes a socket connection the host application will send a string containing ‘CONNECT’ to indicate to the client that the connection is made.

The Client device, upon power-up, continually sends status updates every 2 seconds.

Here’s the problem.

When the host application is bounced the client’s status updates do not reach the host application. The wireshark captures show that, what I consider, a properly formed TCP packet is sent from the client device to the host PC. The host PC replies with a TCP acknowledgement that has a very large ACK value of 429496xxxx. This causes retransmissions and the host PC still responds with an incorrect ACK, this continues indefinitely. The strange thing is that the ‘CONNECT’ message gets successfully sent from the host application to the device, only the messages from the device are not making through to the application. So the socket connection does get made.

A screen capture is shown below. Anyone have any ideas? All help will be appreciated.

Regards,

Mark Weninger, PE
Senior Electrical Engineer
E: mark.weninger@xxxxxxxxx | P: 215 822 4575 | F: 215 822 4372

FMC Technologies, Inc
400 Highpoint Drive | Chalfont, PA | 18914 USA
P: 215 822 4300 | F: 215 822 4553
www.fmctechnologies.com

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