tcp-environ 5 file formats djbwares
tcp-environ UCSPI-TCP environment variables

## Description

The following environment variables describe a TCP connection. They are set up by tcpserver 1, tcpclient 1, and tcp-env 1. Note that `TCPLOCALHOST`, `TCPREMOTEHOST`, and `TCPREMOTEINFO` can contain arbitrary characters and attacker-supplied information.

`PROTO`

  The string `TCP` or `TCP6`, indicating which family of environment variable names to use.

`TCPLOCALHOST`

  The domain name of the local host, with uppercase letters converted to lowercase. If there is no currently available domain name for the local IP address, `TCPLOCALHOST` is not set.

`TCPLOCALIP`

  The IPv4 address of the local host, in dotted-decimal form or the respective compactified IPv6 address.

`TCPLOCALPORT`

  The local TCP port number, in decimal.

`TCPREMOTEHOST`

  The domain name of the remote host, with uppercase letters converted to lowercase. If there is no currently available domain name for the remote IP address, `TCPREMOTEHOST` is not set.

`TCPREMOTEINFO`

  A connection-specific string, perhaps a username, supplied by the remote host via 931/1413/IDENT/TAP. If the remote host did not supply connection information, `TCPREMOTEINFO` is not set.

`TCPREMOTEIP`

  The IPv4 or compactified IPv6 address of the remote host.

`TCPREMOTEPORT`

  The remote TCP port number.

`TCP6INTERFACE`

  The interface name ("eth0") for IPv6 connections using link-local addresses.

`TCP6REMOTEIP`

  The compactified or IPv4-mapped IPv6 address of the remote host.

`TCP6REMOTEHOST`

  Identical to `TCPREMOTEHOST`.

`TCP6REMOTEPORT`

  Identical to `TCPREMOTEPORT`.

## See also

tcpserver 1
tcpclient 1
tcp-env 1
tcp 4

## Author

Original code and documentation by Daniel J. Bernstein. Converted to manual pages and updated by Gerrit Pape in 2000, 2001, and 2002. Converted to DocBook XML by Jonathan de Boyne Pollard.