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Re: [lwip-users] How to get the example tcpecho working on Windows?
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From: |
Gisle Vanem |
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Subject: |
Re: [lwip-users] How to get the example tcpecho working on Windows? |
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Date: |
Sat, 29 Apr 2023 11:25:55 +0200 |
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User-agent: |
Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 |
mengjianshi00@163.com wrote:
Use Wireshark to monitor the traffic between the tcp client ip and the machine running lwip example_app. I notice
sometimes lwip example_app gets a packet but Wireshark doesn't, sometimes Wireshark gets a packet but lwip example_app
doesn't. The SYN packet from the tcp client shows in Wireshark but not in lwip. It's weird because Wireshark uses the
same WinPcap library as lwip does.
Typically this is due to the NIC driver does IP/UDP/TCP checksum
on TX on it's own. Hence an app will see packets with wrong
checksums. (WinPcap and NPcap (?) gets the packets in the
TX-path before the NIC can add the checksum).
Enter the Network card advanced settings dialogue
and turn some/all of these off. Thus forcing Winsock
to do the checksum. You can probably let the RX checksum
offloading be enabled. Depends on your CPU speed.
BTW. please use shorter text-lines next time.
--
--gv