RadioMail can pair with KISS TNC modems to connect to stations via the AX.25 packet protocol.

AX.25 is a protocol used for sending data over amateur radio networks. It is based on the original X.25 protocol, but has been adapted for use in amateur radio. The protocol is designed to provide a reliable means of transmitting data over unreliable radio connections, and includes features such as error detection and retransmission of lost or corrupted data.

KISS TNC modems handle the low level HDLC protocol and signal modulation for transmission over the air.

RadioMail supports zero configuration TNC device discovery as described in those specifications:

• Specification for KISS over BLE (Bluetooth Low Energy)
• Specification for user-friendly DNS-SD discovery of KISS over TCP

Mobilinkd is a portable, battery powered TNC with built-in Bluetooth LE support. To setup a Mobilinkd device, follow these steps:

1. Turn on Mobilinkd. Make sure no other application is paired with the device.
2. In RadioMail, tap Settings -> KISS TNC Modem
3. Tap Default TNC
4. RadioMail will search for nearby devices. When your device appear, tap on its name, for example "TNC3 Mobilinkd"
5. Tap Done

When connecting to packet stations, the default TNC device will be used.

If the device does not show up, make sure that Bluetooth is turned on and that RadioMail has been granted access to Bluetooth. Go to iPhone Settings -> RadioMail and verify that Bluetooth access is turned on.

Depending on your radio setup, some parameters such as Tx delay can be adjusted.

Dire Wolf is a software application that can be used as a virtual TNC for applications such as RadioMail. To setup Dire Wolf, follow these steps:

1. Make sure your version of Dire Wolf includes this DNS-SD enhancement .
2. Start Dire Wolf
3. In RadioMail, tap Settings -> KISS TNC Modem
4. Tap Default TNC
5. RadioMail will search for nearby devices. When your device appear, tap on its name, for example "Dire Wolf TNC"
6. Tap Done

When connecting to packet stations, the default TNC device will be used.

If the device does not show up, make sure that the iPhone WiFi is, is on the same network and that RadioMail has been granted access to local network. Go to iPhone Settings -> RadioMail and verify that Local Network access is turned on.

Depending on your radio setup, some parameters such as Tx delay can be adjusted.

If you have an existing TCP/IP TNC, you have a couple of options.

Option 1: Announce legacy TNC on DNS-SD

You can announce the configuration of your TNC via DNS-SD so that RadioMail can discover it and auto configure its settings. You will need to run the following command on the computer that the TNC is connected to. This has the advantage that if the IP address of the computer changes, it will automatically be published in the local DNS and picked up by RadioMail.

For example, in Linux:

avahi-publish -s "My TNC" _kiss-tnc._tcp 8001 "pn=144.800 1200"

or on a Mac:

dns-sd -R "KISS TNC on the attic" _kiss-tnc._tcp local 8001 "pn=Port 1,Port 2"

Option 2: Specify host and port in RadioMail

Alternatively, you can specify the host name or IP address and port of the computer running the TNC directly in RadioMail. Go to Settings -> KISS TNC Modem -> Default TNC -> Manually configure host and port. Enter the values and tap Done.

Note that if your computer IP address change, you will need to update it in RadioMail.

Digipeaters are special stations that receive and sequentially re-broadcast digital data on the same frequency, extending the range of communications. You can now specify up to two digipeaters to use when connecting to a station in packet or VARA FM mode.

For each mode, you can specify and quickly toggle on or off each digipeater in the Settings interface.

When digipeating is in use, the via path is displayed in the connection dialog, and the DIGI indicator is present.

Note that packet and VARA FM digipeaters are not interchangeable since they need specific knowledge of the protocol to listen to and retransmit the data.