APRS Server

Name

APRS-SRV -- APRS Server.

Description

XRPi includes a rudimentary APRS server, which enables suitable APRS clients, such as UI-View, to connect to it on the LAN and exchange APRS traffic. The number of simultaneous clients is not limited.

TCP Port Number

The server listens for incoming connections on TCP port 1448. There is a tradition of choosing port numbers for APRS servers which represent the frequencies used by APRS, so port 1448 was chosen because XRPi originates in the UK, and many European countries use 144.800 MHz.

Overview Of Server

The following APRS packets are sent to clients:

APRS traffic received by any of XRPi's radio ports.
Traffic sent by other clients.
Traffic sent by users of XRPi's APRS messaging shell.
Filtered traffic from Internet APRS servers (if XRPi's IGATE is connected to an Internet APRS server)

APRS packets from clients are distributed as follows:

To other clients, excluding the sender.
To XRPi's APRS messaging shell.
To radio ports (only if client is fully registered)
To Internet APRS servers via IGATE (if IGATE is running).

Registration and Login

Registration of clients is necessary to prevent unauthorised use of radio frequencies by unlicensed people.

This may seem overly restrictive if your system is only used on a private LAN, but if you are connected to the Internet, it is essential. For example, if an unlicensed user connects to your server via the Internet, he must be prevented from sending traffic to your local RF ports. He must also be prevented from sending traffic via your IGATE (if it is enabled) into the Internet system, and thence to other people's RF ports.

Therefore, clients are required to complete a log-in process before they are allowed to send any traffic. Log-in is not required for receive-only operations.

The server accepts two different types of login. When a user registers an APRS client program such as UI-View, he receives a "validation number" which XRPi uses in combination with the callsign to verify the user. A verified user may send traffic to local RF ports, or if IGATE is active, via other IGATES.

If the user has NOT registered his copy of UI-View, the default validation number of "-1" allows him to send traffic to other clients and to the Internet, but that traffic will not be gated locally to RF, and is marked in such a way that it will not be gated to RF by other IGATES. This allows unregistered clients to communicate with each other via the Internet, but not via RF. The client may only send APRS packets whose source callsign matches the login callsign.

The alternative login system allows clients to verify themselves by supplying their callsign and a password which has been agreed with the sysop. The password replaces the validation number in a login string.

The login string is the only "command" accepted by the server, and must take the form: "user <callsign> pass <password>", where <password> could be either a validation number or a text string, for example,

	"user g8pzt pass beanzmeanzheinz", or
        "user g7zzz pass 32751".

The Client Connection

There is no time-out on client connections, therefore there is no need for the client to send "keep-alive" signals.

If the client connection is too slow to cope with the incoming data rate, packets to the client may be discarded.

Local <> Internet Server Gating

If IGATE is not running, no packets are gated to or from the Internet.

Packets received from the Internet are not gated to clients unless they satisfy the IFILTER (Internet Filter) filtering rules in IGATE.CFG. Likewise, packets received from clients are not gated to the Internet unless they satisfy the PFILTER (Packet Filter) rules.

The following traffic is NOT gated from RF to Internet

Packets in "third party" format.
Packets which do not include the network identifier "TCPIP" in the digi path.
Packets which include the dummy callsigns NOGATE or RFONLY in the digi path.

Using UI-View as a Client

Select Setup/APRS Server Setup.

In the box marked "Select A Server", enter the hostname and TCP port number of XRPi's APRS server, e.g. "myserver:1448" or "192.168.0.2:1448". If the client is on the same computer as XRPi, use "localhost:1448" or "127.0.0.1:1448". (If you use a private hostname, you may need to add a suitable entry into the HOSTS file in the WINDOWS directory.)

Check the boxes marked "Open the gateway" and "Gate local messages".

If you have a registered version of UI-View, check the box marked "APRServe log on required", and enter your validation number.

If your copy of UI-View is unregistered, you will be able to log on to XRPi's APRS server with the default validation number of -1, but your packets will not be gated to RF.

To obtain full privileges using an unregistered copy, you must have a password, which must be registered with your callsign in XRPi's USERPASS.SYS file. The callsign must not include the SSID, e.g. if UI-View's callsign is "G8PZT-11", the entry in USERPASS.SYS should simply be "G8PZT". Un-check the "APRServe log on required" box, and in the box marked "Text to send upon connection" enter UI-View's callsign (with SSID) and your password in the following form:

	user g8pzt-11 pass virago

See also

APRS(9) -- APRS in XRPi.
IGATE(9) -- APRS Igate.
IGATE.CFG(8) -- Igate Configuration File.
TCP-PORTS(6) -- TCP Service Ports.
USERPASS.SYS(8) -- User Passwords File.
XROUTER.CFG(8) -- Main Configuration File.