freebsd man page for tcpdrop

TCPDROP(8)						    BSD System Manager's Manual 						TCPDROP(8)

NAME
     tcpdrop -- drop TCP connections

SYNOPSIS
     tcpdrop local-address local-port foreign-address foreign-port
     tcpdrop [-l] -a

DESCRIPTION
     The tcpdrop command may be used to drop TCP connections from the command line.

     If -a is specified then tcpdrop will attempt to drop all active connections.  The -l flag may be given to list the tcpdrop invocation to drop
     all active connections one at a time.

     If -a is not specified then only the connection between the given local address local-address, port local-port, and the foreign address
     foreign-address, port foreign-port, will be dropped.

     Addresses and ports may be specified by name or numeric value.  Both IPv4 and IPv6 address formats are supported.

     The addresses and ports may be separated by periods or colons instead of spaces.

EXIT STATUS
     The tcpdrop utility exits 0 on success, and >0 if an error occurs.

EXAMPLES
     If a connection to httpd(8) is causing congestion on a network link, one can drop the TCP session in charge:

	   # sockstat -c | grep httpd
	   www	    httpd      16525 3	tcp4 
		   192.168.5.41:80	192.168.5.1:26747

     The following command will drop the connection:

	   # tcpdrop 192.168.5.41 80 192.168.5.1 26747

     The following command will drop all connections but those to or from port 22, the port used by sshd(8):

	   # tcpdrop -l -a | grep -vw 22 | sh

SEE ALSO
     netstat(1), sockstat(1)

AUTHORS
     Markus Friedl <markus@openbsd.org>
     Juli Mallett <jmallett@FreeBSD.org>

BSD
								 January 30, 2013							       BSD