Connect your terminal to POS

This guide covers the local link between your POS and the terminal: how they physically connect, which port to use, and the terminal-side setup. Host-side steps live in a separate guide per operating system. For the terminal's IP address and firewall access to Market Pay, see Configure your network.

Choose a connection topology

Decide how the POS and terminal connect, and how the terminal reaches the internet:

Topology USB Mode Internet connection How it works
Serial communication over USB USB n/a not supported 
Network only n/a RJ45, Wi-fi The terminal is assigned an IP by your network; the POS, on the same network, reaches it at that address.
TCP/IP over USB with internet sharing USB-PC (RNDIS reverse), 
USB ECM-HOST tethering		 USB USB carries POS↔terminal messages (fixed IP 192.168.42.129) and internet connection 
TCP/IP over USB without internet sharing USB ECM tethering, USB tethering (RNDIS) RJ45, Wi-fi USB carries POS↔terminal messages only (fixed IP 192.168.42.129); 

Tip

We recommend the TCP/IP over USB topology — Ethernet for internet and USB for POS↔terminal messages. A network hiccup then won't interrupt communication between the POS and the terminal.

Which port to use?

The port depends on how the terminal is locked down and which transport you use:

Port Use
7778 Standard. Used with our Master Application (integrated mode), where the terminal is locked down to accept payment requests only from the ECR.
7777 Used without the Master Application (mixed mode), where the Payment Application can also be used standalone to enter amounts manually.
8080 HTTP (Local API) integration.

Note

The Master Application (launcher) blocks access to the Android menu, settings, and payment app for the customer — the common setup for terminals in supermarkets or on self-checkout, where usage is limited to operations from the POS.

Verify connectivity

Confirm the terminal can reach the internet from the Pay On Site application:

  1. Open Pay On Site.
  2. Tap the three lines at the top left, then Configuration → Diagnosis.
  3. The Diagnosis screen reports whether the terminal has connectivity.

If Pay On Site has not been activated yet, go into OS settings, check if terminal has an IP Address assigned.

Tip

If Diagnosis fails, re-check that the host adapter IP is 192.168.42.1, that internet sharing points at the terminal's RNDIS adapter, and that the terminal's gateway matches the host adapter IP.

Next steps