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I'm having an issue with a tcp handshake that I can't find the answer to anywhere else.

I have a program running on my local device that posts data to port 50000. In a terminal on the same machine, I use netcat to connect to the port. However, while using tcpdump and wireshark, I can see that the SYN packets are sent but the SYN/ACK packets are never sent in response. My iptables have no rules for connections, and the default policy for all chains is to accept the connection. This happens every time I try to connect, and so far I can't see why the server is not responding to the SYN packets.

Austin
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1 Answers1

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I fixed it. To my dismay, it actually was a code issue. We set our listen() backlog size to 0, causing any attempted connection to fail. In the case of TCP this meant retransmitting the packets. Don't know how this worked on one machine and not the other, but now they both work. Thanks for the comments everyone.

Austin
  • 141