Established TCP handshake but nothing happens after

asked 2025-08-10 01:01:28 +0000

Wireshark77 gravatar image

updated 2025-08-10 01:53:40 +0000

Chuckc gravatar image

I've written my own network stack and I am connecting to www.nossl.com (I was trying to find a server which would return plaintext, not SSL).

My TCP handshake seems to complete but I don't receive any more packets (data) afterwards. I am expecting to receive some of the web page bytes.

The handshake:

53  5.031672991 192.168.1.100   23.239.3.134    TCP 54  23468 → 80 [SYN] Seq=0 Win=65535 Len=0
54  5.179647283 23.239.3.134    192.168.1.100   TCP 60  80 → 23468 [SYN, ACK] Seq=0 Ack=1 Win=64240 Len=0 MSS=1452
55  5.180177911 192.168.1.100   23.239.3.134    TCP 54  23468 → 80 [ACK] Seq=1 Ack=1 Win=65535 Len=0

After this I don't receive any more packets to port 23468.

Can anyone please advise what I may need to check? My second transmitted packet contains no checksum errors etc.

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Comments

If I change the server address to www.neverssl.com, I send my initial SYN but I don't even receive a SYN-ACK back. Same code. Wireshark says the checksum was good, only flag set is SYN. No obvious errors.

Wireshark77 gravatar imageWireshark77 ( 2025-08-10 01:10:05 +0000 )edit

Try curl or wget or ncat and capture with Wireshark to see a working example.

Chuckc gravatar imageChuckc ( 2025-08-10 01:57:40 +0000 )edit

You are connecting to a HTTP server, do you ever send a GET request?

Jaap gravatar imageJaap ( 2025-08-11 03:26:46 +0000 )edit
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