I’m attempting to ascertain a TCP reference to a server. I added a firewall rule within the server to drop the TCP packets so as to examine how the TCP consumer terminates.

Consumer retransmits SYN a number of occasions and won’t obtain SYN+ACK and eventually the consumer terminates. I might solely see SYN retransmissions within the tcpdump and there was no FIN or any indications on the way it closed. So, does the consumer terminate silently with out sending out any closure packet on this case?

And what number of occasions a TCP SYN is retransmitted?

1

… there was no FIN or any indications on the way it closed

A FIN is used to sign to the peer that the connection will get closed. Because the connection was by no means established within the first place, no FIN is distributed to shut it.

And what number of occasions a TCP SYN is retransmitted?

This is determined by the system and its tuning. For instance in Linux there may be tcp_syn_retries:

tcp_syn_retries (integer; default: 6; since Linux 2.2)
The utmost variety of occasions preliminary SYNs for an energetic TCP
connection try will likely be retransmitted. This worth
shouldn’t be larger than 255. The default worth is 6,
which corresponds to retrying for as much as roughly 127
seconds. Earlier than Linux 3.7, the default worth was 5, which
(at the side of calculation based mostly on different kernel
parameters) corresponded to roughly 180 seconds.