Server responds to SYN with additional ACK

[baukran]

Hi,

I am using OMNeT++ 5.1 and installed INET.

I'm establishing a TCP connection and always drop the SYN+ACK response of the server.

Beginning with the first retransmission of the SYN, the server also besides sending a SYN+ACK sends an ACK as well.

Is this  behaviour correct?

I attached a screenshot which shows this.

Best regards

baukran

[baukran]

I think this behaviour is correct. The server retransmits its SYN+ACK since it receives no ACK. When it receives SYN, it ACKs it.