Moxa NPort 5210A

Moxa · serial device server, 2 ports · NPort 5210A

what it is

A serial device server: two RS-232 ports on one side, the network on the other. It turns a device that can communicate only over a serial cable into a device reachable over the network.

In practice it is a way to handle equipment older than the IP protocol — controllers, scales, readers, UPS units, consoles of network devices. Without such an intermediary you have to walk up to them with a laptop.

In Real COM mode the manufacturer's driver creates virtual COM ports in Windows that lead over the network to the NPort's ports. Each port then has its own data port and command port.

Metal enclosure, 77 × 111 × 26 mm without mounting ears (100 mm with ears), weighing 340 g. DC power 12–48 V, via two independent inputs: a barrel jack and a removable three-pin terminal block. It neither accepts nor supplies PoE — the power section of the datasheet lists two inputs and there is no third among them.

There is one network port, 10/100, with 1.5 kV magnetic isolation. For devices connected to industrial machines this is not an embellishment: the isolation stands between the network and anything that may come from the machine side.

Watch out for the siblings. The same series includes the NPort 5230A (two terminal blocks instead of DB9 connectors, because RS-422/485) and the NPort 5250A (the same DB9 connectors, but RS-232/422/485). A separate device is the NPort 5210 without the letter A — a different series, a different enclosure.

what we read from it

• Number of serial ports and how many of them are in use. A serial port has no "link" in the network sense, so this is the only information on whether anyone is using it at all.
• Firmware version and the system name set on the device.
• Uptime since power-on. For an intermediary standing between the network and a machine, a restart is sometimes the only trace of a power loss on the machine side.
• The full set of network link data: negotiated speed, duplex, medium, port number on the switch, transmit and receive error counters along with the per-minute increase, the number of link drops, spanning tree changes and a link quality assessment.
• Transmitted and received traffic.
• Availability and response latency.

port layout

The drawing shows both panels. On the front there are two male DB9 connectors, spaced just under five millimeters apart, with screw standoffs on the sides. The manufacturer numbers them "Port 1" and "Port 2" and labels its own drawing the same way.

On the rear panel, from the left: the barrel power jack, the removable three-pin terminal block (the second, independent power input), the network port and a pin-operated reset hole.

The network port has no number on the enclosure — the manufacturer numbers only the serial ports.

what to watch out for

• Bytes arrive but are unreadable — that is a wrong baud rate, not a damaged console or a bad cable. Garbage proves the link works. In Real COM mode, setting the speed on the virtual COM port reconfigures the NPort by itself.
• The correct speed is settled by the echo, not by whether anything arrived at all: at the right speed exactly what was sent comes back.
• Each port serves one client at a time. A port held by the Real COM driver or open in a terminal program looks closed in a port scan.
• In firmware 1.7 the SNMP form in the web panel cannot be saved — a script error on the page blocks the button even in a regular browser. Enabling SNMP by bypassing the form leaves a community that cannot be guessed; the reliable way is the manufacturer's NPort Administrator tool.
• Logging in to the web panel is a challenge-response computed by a script in the browser, not a plain password in a form. Simple tools without a browser will not log in.

what we cannot read

• What is connected to the serial port or whether it responds. The device forwards bytes and does not understand their content — that is a hardware limit.
• Which of the two power inputs is currently in use.
• Temperature.

full parameter list

A full parameter list for this model is not here yet — the ones described above are those we have read and verified. A missing list does not mean the device exposes nothing more.