how to close an established network connection in linux and osx

Question

I used to do this in the Windows world with tool called TCPView: just select a established connection (ESTABLISHED), then select "Close Connection". I can't find a way to this on Mac OSX or Linux (I need both). The only way I know of is to kill the process that has the port open.

My main use case is to simulate interruptions in connectivity to test failover, like unplugging a cable or losing a router or middleware situations.

Answer 1

You could attach to your process using gdb and close() the file descriptor corresponding to the connection. You can find out the file descriptor number using lsof -a -i4 -p $PID.

Answer 2

• tcpkill -i eth0 { expression }
  (basic command/options)

• tcpkill -i eth0 port 21
  (Kill all outgoing ftp (port 21) connection)

• tcpkill host 192.168.1.2
  or
  tcpkill host hostname.domainname.com
  (Kill all all packets arriving at or departing from host 192.168.1.2)

• tcpkill ip host 192.168.1.2 and not 192.168.1.111
  (To kill all IP packets between 192.168.1.2 and any host except 192.168.1.111)