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I have a port server that converts an 19.2kbps rs-232 data stream to tcp/ip then to my computer wirelessly using Motorola Canopy system. When my tcp/ip server software connects to the end device (the serial device), the available bandwidth is reduced drastically. Here is a screen shot of the bandwidth usage when connected to two port servers:

See Attached Image 1
(My computer IP is .140 and the two serial port server IPs are .101 and .102)


I used wireshark to have a look at the packets being sent accross the network. It seems that the network conjestion is being cause by a Duplicate Acks sent by my computer. Here is a picture of the wireshark capture:


See Attached Image 2
(My computer IP is .140 and the two serial port server IPs are .101 and .102)

What are possible explainations of so many duplicate acks being sent. What else can I do to trouble shoot the problem?


Thanks so much for any help as I have been scratching my head for days on this one:)

networkAnalysis_secure.gif 16.75 KB wireshark_secure.jpg 676 KB
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Okay, I finally found the problem. The serial port server was not buffering data before sending it TCP, instead it was just sending small packets of data and that flooded the network. Fixed problem by increasing data buffer size on port server.

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