Need help getting started working with a serial server

Serial Communication
1

I’m trying to set up and work with a serial server for the first time and I’m confused about how to configure it, connect devices, and test communication. The documentation is pretty vague, and I’m not sure which settings or tools I should be using for reliable data transfer. Can someone walk me through the basics or share best practices for working with a serial server in a small network setup?

2

First time with serial servers is kinda like first time in BIOS: bunch of scary settings, nothing labeled in plain english, and somehow it still works if you don’t break too much.

Here’s a way to tackle it step by step.

1. Basic concept check

A serial device server just takes a physical COM port (RS‑232/485/422) and exposes it over TCP/IP. On your PC you use a “virtual COM port” so your old serial app thinks it is still talking to COM3 or whatever.

If you want to do this in software instead of a hardware box, have a look at something like easy serial device server software for remote COM ports. That kind of app basically gives you a software serial server. Their “Serial to Ethernet Connector” is one of those tools that lets you map a local virtual COM to a remote TCP port, so the OS and apps don’t know or care it is over the network.

2. Hardware side first

  1. Figure out what you’re plugging in: RS‑232 or RS‑485/422.

    • RS‑232: point to point, DB9 or DB25, usually 3 wires (TX, RX, GND).
    • RS‑485: 2‑wire or 4‑wire, A/B lines, often multi‑drop.

  2. Cabling:

    • For RS‑232, if you are going PC to serial server, it is usually straight through. If talking to another DTE type device you may need a null modem cable.
    • For RS‑485, mind polarity, termination resistor, and biasing.

  3. Power up the serial server, stick it on the same LAN as your PC.

3. Network config

Typical stuff in the web UI of the hardware server:

  • Assign static IP, subnet, gateway.
  • Decide access mode: “TCP server” mode is the usual starting point. It will listen on a port like 4001.
  • Disable anything “fancy” for now: no encryption, no special protocols. Just raw TCP.

Write down:

  • IP address of the serial server
  • TCP port number for that COM port

4. Serial port settings

Match these EXACTLY to the device you are talking to:

  • Baud rate (9600 / 19200 / 38400 etc)
  • Data bits (usually 8)
  • Parity (None, Even, Odd)
  • Stop bits (1 or 2)
  • Flow control (None, RTS/CTS, XON/XOFF)

If you don’t know them, try to dig them from the device manual. Guessing is a time sink. 9600 8N1 no flow is the most common default, but don’t rely on that forever.

5. PC side test without virtual COM

Before you drag in extra software:

  1. Use PuTTY, Tera Term, or similar.
  2. Select “Raw” or “Telnet” mode and connect to:
    • Host: the IP of the serial server
    • Port: that TCP port for the serial channel

If your serial device sends periodic data, you should see it in the terminal. If not, try sending its known command (from the manual) and see if it responds.

If that works, the server and serial wiring are OK.

6. Add virtual COM if your app requires a COM port

If your old software insists on COM1/COM2:

  • Install something like Serial to Ethernet Connector.
  • Create a “client” connection to the IP and TCP port of your hardware serial server.
  • It will give you a virtual COM port, say COM5.
  • Configure your legacy app to talk to COM5 with the right serial settings.

Result: app thinks it is local serial, but it is actually going across the net.

Same thing if you forgo the hardware box and just want a pure software “serial device server” setup on a PC that shares its local COM with other machines on the network. That’s exactly the use case for a Serial to Ethernet Connector type tool.

7. How to know what’s wrong

Quick troubleshooting tree:

  • Can you ping the serial server IP?
    • No: network issue, VLAN, firewall, wrong IP.
  • Can you open a TCP connection to the port with telnet IP port or PuTTY?
    • No: port blocked, server config wrong, listening on different port.
  • TCP ok but no serial data:
    • Serial wiring or wrong RS‑232 vs RS‑485.
    • Baud / parity / stop bits mismatch.
    • Flow control misconfigured.
  • Sporadic garbage characters:
    • Usually baud or parity mismatch.

8. Minimal checklist so you don’t go in circles

  • Confirm physical interface type and cable
  • Set known IP and port on the serial server
  • Match all serial parameters to the device
  • Test with PuTTY/Telnet first
  • Only then add any virtual COM solution like Serial to Ethernet Connector
  • Add security, firewalls, VPNs after it works in basic mode

If you post the exact model of the serial server and the serial device type, plus what you’ve already tried, folks here can probably tell you exactly which settings to flip and which “helpful” defaults to kill.

Need help getting started working with a serial server
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3

First thing: don’t panic, everyone’s first serial server feels like “congrats, here’s 40 ways to fail silently.”

@viajeroceleste already nailed the classic step‑by‑step. I’ll try to fill in the gaps they didn’t touch and disagree in a couple spots where I think beginners get tripped up.

1. Start with a loopback test (even before the real device)

Instead of going straight from “mystery device” to “mystery server,” isolate stuff:

  1. On the serial server, plug in a short loopback:

    • RS‑232: jumper TX to RX (pins 2 and 3 on DB9) and tie GND to GND.
    • RS‑485: connect A to B through a resistor only if the manual suggests it, otherwise just use a real device here.

  2. From your PC, open a TCP client (PuTTY in Raw mode is fine) to the server IP and port.

  3. Type characters.

    • If you see exactly what you type echo back, the server’s serial port + TCP side is working.
    • If nothing comes back, you have a server config or cabling issue before you even drag your actual device into this.

I actually prefer this over directly testing with the final device, because it narrows the problem to “server + network” vs “device + protocol.”

2. Ignore “auto” features at first

Where I slightly disagree with the “just disable fancy stuff”: some serial servers ship with “auto baud” or “packetization / idle timeout / delimiter based transmission” features silently enabled.

For a beginner, those are confusing as hell, so:

  • Turn OFF:
    • Auto‑baud detection
    • Any “packet size” or “idle timeout” transforms
    • Any “Telnet IAC” options
  • Make it behave like a stupid pipe: raw bytes in, raw bytes out.

In the docs, this is often hidden in “advanced” or “packing” or “data framing” sections.

3. Decide your “direction of truth”

You have two sets of settings that must match:

  1. Serial server port
  2. End device (PLC, sensor, scale, etc.)

Pick one as the “truth.” Normally that should be the device, since its parameters may not be easily changeable. Then:

  • Configure the serial server to match the device exactly.
  • Do not randomly change both ends while testing or you’ll chase ghosts.

If you really don’t know the device settings and the docs are useless, try in this order:

  • 9600 8N1 no flow
  • 19200 8N1 no flow
  • 38400 8N1 no flow

Change only one thing at a time, test, then move on.

4. Watch signals, not just data

If your serial server exposes modem control lines (RTS, CTS, DTR, DSR), check its web UI or status page:

  • CTS stuck low and you have hardware flow control enabled: your device will never talk.
  • If you are not explicitly using flow control, force:
    • Flow: None
    • And if possible, tie RTS/CTS together on the cable or use a “no handshake” cable.

A lot of people waste an entire afternoon because the default is RTS/CTS but the device expects no flow control.

5. When to use a virtual COM vs direct TCP

Here is where I don’t 100% agree with starting always with a terminal:

  • If your main application absolutely expects a COM port and does weird timing / control signaling, sometimes virtual COM (Serial to Ethernet Connector or similar) behaves closer to what the app expects.

My suggestion:

  1. First check raw TCP with a terminal like @viajeroceleste said, just to prove “bytes move.”
  2. If your real software:
    • Only lists COM1…COMx
    • Has no TCP config
      then bring in a virtual COM tool.

In that case, something like Serial to Ethernet Connector is pretty handy, because it lets you:

  • Create a virtual COM port that maps to TCP: server_ip:port.
  • Keep all your serial settings centralized.
  • Share local hardware COM ports over the network if needed.

That way, from the app’s point of view, it is just talking to COM7 like always.

If you want to grab a build, this is a decent starting point for installation packages and tools:
find the latest Serial to Ethernet tools and installers here

6. Test pattern instead of random typing

Once you think it’s working, send a recognizable test sequence, like:

  • ASCII: HELLO12345\r\n
  • Or hex: use a tool that can send hex frames so you know exactly what bytes you generate.

Reason: if you get “HÉLLo1#5” back, that screams wrong baud or parity. Random text is harder to eyeball for subtle corruption.

7. Logging is your friend

Most half decent serial servers have:

  • Syslog or event logs
  • Per port statistics: bytes sent, bytes received, framing errors, parity errors

Check those:

  • Parity or frame errors going up: mismatch in serial settings or really bad cabling.
  • Bytes TX from TCP but zero RX on serial: device not responding, wrong wiring, or wrong RS standard.

Keep one terminal tailing logs while you test so you catch errors live.

8. Minimal setup recipe you can try right now

  1. Pick one port on the serial server.
  2. Set:
    • Mode: TCP server
    • Port: 4001 or whatever you like
    • Serial: 9600 8N1, no flow
  3. Connect loopback on that port (or your device if you’re brave).
  4. From your PC:
    • ping the IP
    • Then PuTTY Raw to IP:4001
  5. Type “TEST123”:
    • Loopback: you should see “TEST123” echo back.
    • Real device: check its manual for a simple query command and try that.

If that works, then start tightening security, changing baud, and wiring more devices.

If you post model of the serial server and what device you’re trying to talk to plus what you’ve tried so far (baud, parity, wiring type), people can usually point at the exact checkbox or setting that’s messing you up. Right now you’re probaby one or two parameters off from it just working.

Need help getting started working with a serial server
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4

Skip the generic stuff already covered by @vrijheidsvogel and @viajeroceleste; they nailed the fundamentals. I’ll zoom in on decision points that usually hurt first‑timers.

1. Pick the right “mode” on the serial server

Most serial servers offer several modes that look similar but behave differently:

  • TCP Server
    Listens on a port. Good when you have one client connecting (your PC or a virtual COM).
  • TCP Client
    The serial server initiates the connection to a known host/port. Good if your PC is behind NAT or firewall and you want the serial end to “call home.”
  • UDP
    Best avoided at first. No guarantee of delivery, debugging is harder.
  • RFC2217 / COM redirector / “remote COM” mode
    Lets a virtual COM driver control serial parameters over TCP.

If you just want “PC on same LAN talks to device,” I’d disagree a bit with jumping straight into anything fancy: start with TCP Server and a single client only, and disable multi‑client or UDP broadcast features that many devices enable by default.

2. Protocol vs transport: don’t mix concerns

A lot of confusion comes from mixing serial settings with the application protocol on top:

  • Serial layer: baud, parity, stop bits, flow control.
  • Protocol layer: Modbus RTU, ASCII commands, proprietary binary.

You can have the serial link absolutely perfect and still see nothing if:

  • You expect Modbus but the device speaks proprietary ASCII.
  • The device needs a specific wake‑up command or login before sending data.

So when you “see nothing” in PuTTY connected to the TCP side:

  1. Confirm the device is supposed to talk spontaneously. Many do not.
  2. If it’s Modbus RTU, you will never get human‑readable text. Use a Modbus master tool to query, not a plain terminal.

This is where tools like Serial to Ethernet Connector help because you can let a proper protocol master (Modbus client software, vendor config tool, etc.) talk to a virtual COM as if it were local, instead of trying to “speak” the protocol manually in a raw TCP terminal.

3. When to choose Serial to Ethernet Connector vs built‑in redirectors

Your serial server vendor might ship its own COM redirector. Those work, but they are often:

  • Vendor specific
  • Clunky to manage on many PCs
  • Weak on logging and diagnostics

Serial to Ethernet Connector is more general purpose. Short pros/cons from a practical angle:

Pros

  • Works as a generic virtual COM client to any serial server that exposes a TCP port.
  • Lets you share real hardware COM ports from one PC to another over the network.
  • Usually nicer UI for seeing which PC is connected to which remote port.
  • Can be handy if you later ditch the hardware serial server and just share a local COM from a single host.

Cons

  • Extra piece of software to install and maintain.
  • Another possible failure point in the chain.
  • License cost vs the free, albeit basic, redirectors some serial servers include.

Compared with the approaches discussed by @vrijheidsvogel and @viajeroceleste, using Serial to Ethernet Connector makes particular sense if:

  • You have multiple PCs that all need to access the same serial device.
  • You want centralized management of serial links, instead of configuring every client with a different redirector.
  • You want to move away from a specific brand’s tools and keep things vendor neutral.

4. Testing technique that avoids false positives

A small disagreement with relying on simple text echoes as the final check: it proves bytes flow but not that timing and framing are right for the real application.

For better confidence:

  1. Get the real application or vendor tool that will use the serial link.
  2. Connect it through Serial to Ethernet Connector to the serial server’s TCP port.
  3. Use the app’s “identify device” or “read config” function.

If that works reliably across several operations, your full stack is good:

PC app → virtual COM → TCP → serial server → serial wire → device

If only PuTTY works but the real app is flaky, suspect:

  • Latency / packetization timing in the serial server
  • Flow control mismatch
  • Too aggressive “data packing” options (disable thresholds and timeouts or set them as loose as possible)

5. Checklist for your next concrete step

Given what’s already been suggested, here’s a minimal next move list that adds value rather than repeats:

  1. Decide: are you going to reach the server as TCP Server from the PC, or do you need the opposite (TCP Client mode) because of network constraints?
  2. Confirm what protocol your field device speaks. If Modbus RTU or some binary protocol, stop expecting readable text in terminals.
  3. Configure the serial server in simple TCP Server mode, no packetization, no auto‑baud, no Telnet options.
  4. Install Serial to Ethernet Connector on your PC and create a virtual COM pointed at IP:port of the serial server.
  5. Point your actual device software at that virtual COM and test a real operation, not just manual typing.
  6. If it half‑works or is unstable, look specifically at:
    • Flow control settings
    • Error counters in the serial server (parity, framing, overrun)
    • Any “max connections” or idle timeout options that might close the TCP link mid‑session.

If you share the exact device type and protocol (for example “scale with ASCII line protocol” or “PLC using Modbus RTU”), people can help pick precise serial parameters and server options instead of guessing.