Is it possible to find whether the firewall (iptables) or tcpwrapper is blocking a connection without accessing the remote server? (Maybe with tcpdump?)
What is blocking: Firewall and tcpwrapper?
networking;iptables;tcp wrappers
The IP network layer doesn't know if a tcpwrapper is blocking the connection. Even when tcpwrapper blocks, the network port will appear as open. Example with sshd being blocked via hosts_access:$ nc -w1 -v -z host.example.org 1234nc: host.example.org (192.168.0.130) 1234 [1234] open$ ssh -p 1234 host.example.orgssh_exchange_identification: read: Connection reset by peerA IP based firewall on the other hand would (in most cases) block the connection on the network level and the port would appear as closed.