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Man Pages

Manual Reference Pages  -  DTCPCLIENT (8)


dtcpclient - Dynamic Tunnel Configuration Protocol client


Return Values
Parameters Passed To Scripts
See Also


dtcpclient [-b udp-port] [-B nat-port] [-d] [-D] [-f pidfile] [-l] [-m mtu] [-n] [-p port] [-s script] [-t tuntype] [-u user] [-U] server


dtcpclient implements Dynamic Tunnel Configuration Protocol (DTCP for short) proposed by Trumpet. dtcpclient will first ask the DTCP password to the user. Then, the program will try to connect DTCP server via IPv4 TCP, login as DTCP client, and maintain IPv6 over IPv4 tunnel connection.

The following options are available:
-b port
  Sets the port number to bind on local for an UDP tunnel to port. The default is "4028".
-B port
  If you are behind NAT which is statically configured to forward the UDP tunnel traffic arrived to the specific port, sets the port number to port. This option is meaningful only with -U option, and is usually used with -n . The default is not defined.
-D dtcpclient becomes daemon.
-d Put dtcpclient to debug mode.
-f file
  If dtcpclient is invoked as daemon, the process ID of the dtcpclient are held in /var/run/ by default. You may want to change the file name.
-l By default, when connection to the server is closed, dtcpclient will exit. When this option is specified, dtcpclient doesn’t exit on connection close, and continuously tries to re-connect.
-m mtu Sets the MTU of the tunnel to mtu. The default is "1280".
-n By default, dtcpclient checks if the IPv4 address which DTCP server recognized is equal to the actuall IPv4 address of your box. This check can be ommitted by specifying this option. It may save the user lives behind NAT that maps private IPv4 address to global IPv4 address.
-p port
  Sets the port number to port. The default is "20200".
-s script
  Specify the command to invoke on DTCP session is established or closed. The default is /usr/local/etc/dtcpclient.script.
-t tuntype
  The spec defines several kind of tunnel requests. dtcpclient will request tunnel typed tuntype to the DTCP server. "tunnelonly", "host" and "network" are available for tuntype. The default value is "tunnelonly".
-u user
  Specifies the user. It is needed when DTCP user account is different from the login name on the host.
-U By default, dtcpclient creates a generic tunnel. If this option is set, dtcpclient creates an IPv6 over an UDP/IPv4 tunnel instead. An IPv6 over an UDP/IPv4 tunnel requires Netgraph. (Experimental)
  DTCP server which dtcpclient try to connect.

Upon receipt of signal SIGHUP, dtcpclient will try to reconnect to the DTCP server.


dtcpclient will exit with positive value on errors.


The invoked scripts get passed these parameters:
state Why this script is called. Possible state are "up" and "down".
server DTCP server which dtcpclient connect to.
myaddr My actuall IPv4 address.
tuntype The tunnel type. The value is one of "tunnelonly", "host" or "network"
me My IPv4 address which DTCP server recognize.
her The destination IPv4 address of the tunnel.
me6 The IPv6 address for local tunnel end point if this is a "host" tunnel type or numbered tunnel when tunnel type is "network".
her6 The IPv6 address for remote tunnel end point if this is a "host" tunnel type or numbered tunnel when tunnel type is "network".
prefix The IPv6 prefix assigned to local network when this is a "network" tunnel type .


  You can specify your password to connect to DTCP server in this file. If your password is found in this file, dtcpclient does not ask for your password. The format is a colon-separated list of the server name, the user name and the password.
  Default script invoked for setup or cleanup tunnel when DTCP session is established or closed.
  Contains the process ID of the dtcpclient listening for connections. The content of this file is not sensitive; it can be world-readable. This file name may be changed by -f option.




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dtcpclient will not work if you are behind a NAT box ( This is a protocol feature, not a bug ). -n may help you on such case. But, it is still depend on the behavior of your NAT box.
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