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P4 Server Administration Documentation | 2025.1

# Use P4PORT to control access to the server

Under most circumstances, your P4 Server’s `P4PORT` setting consists of a port number. Users must know the IP address (or be able to resolve it from a hostname) of the P4 Server in order to connect to it.

The value of `P4PORT` however, can also include an IP address or hostname that resolves to an IP address. You can set `P4PORT` to configure the following possibilities:

- `P4PORT=`portnumber``

  In this case, the server listens on the specified port for every IP address associated with this host.

- `P4PORT=`ipaddress`|`hostname`:`portnumber``

  In this case, the server listens on the specified port for the specified IP address or host name, and it ignores requests to any other IP address.

- `P4PORT=localhost:`portnumber``

  In this case, the server listens on the specified port for requests that originate from users on this host. This forces the P4 Server to ignore all non-local connection requests.

P4PORT might also specify a protocol (``protocol`:`address`:`port``), which further restricts possible connections to those using the specified protocol. For complete information, see `P4PORT` in the P4 CLI Reference.

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