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 How it works Use it when
USB only USB is turned into a TCP/IP link (RNDIS or ECM); the terminal also reaches the internet through the USB host. The ECR reaches the terminal at the fixed IP 192.168.42.129. You have a single till/PC and want one cable for both messages and internet.
Network only (Wi-Fi, RJ45) The terminal is assigned an IP by your network; the ECR, on the same network, reaches it at that address. The terminal and POS share a LAN.
Mixed (recommended) USB carries POS↔terminal messages (fixed IP 192.168.42.129); a separate Ethernet or Wi-Fi link carries the internet. You want the most reliable setup.

Tip

We recommend the Mixed 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.

Configure the terminal for USB

This section runs on the terminal itself and is the same whatever host operating system you use. It exposes the terminal as a USB network card (RNDIS reverse) and gives it an IP the POS can reach. Do this first, then configure the host below.

Step 1 — Open the terminal apps

Press the green button several times in a row until the terminal prompts for a password, then enter pax9876@@. The management applications appear, including NTMS Agent.

Step 2 — Enable the USB network card (RNDIS reverse)

  1. Open NTMS Agent, which holds all USB configuration.
  2. Go to Advanced settings and enter the password 4315. You only need two entries here: ETH over USB Settings and USB Mode Settings.
  3. Open USB Mode Settings, select USB-PC (RNDIS reverse), and save. This is what makes the terminal show up as a network card on the host.
Terminal USB connection settings

Step 3 — Set the terminal's USB IP

Back in Advanced settings, open ETH over USB Settings. Change the interface from ecm0 to rndis0, then set:

  • IP — the address the terminal will hold on the USB link (default 192.168.42.129).
  • Netmask — 255.255.255.0.
  • Gateway — the IP you will give the host's USB adapter (192.168.42.1).

Note

The terminal IP and the host USB-adapter IP must sit in the same subnet, with the host acting as the terminal's gateway. If you keep the defaults, the POS reaches the terminal at 192.168.42.129 and the host adapter is 192.168.42.1.

Set up the host connection

With the terminal in RNDIS reverse mode, configure the host to talk to it and to share internet over the USB link. Follow the guide for your host operating system:

Host OS Guide
Windows Configure a Windows host for USB and Ethernet — internet sharing (RNDIS), persistence, and Ethernet.
Linux (Ubuntu) Configure a Linux host for USB (RNDIS reverse) — IP forwarding, iptables NAT, and USB interface IP.

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.

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