Port 1861: LeCroy VICP — The oscilloscope's network port

Port 1861 is assigned by IANA to VICP — the Versatile Instrument Control Protocol, a proprietary TCP/IP protocol developed by Teledyne LeCroy for remote control of their oscilloscopes.¹

What It Does

When a LeCroy oscilloscope is connected to a network, it listens on port 1861 for VICP commands. Software running on a computer — whether a custom script, LabVIEW, MATLAB, or LeCroy's own tools — connects to this port and sends commands to control the scope: start acquisitions, change timebase settings, pull waveform data, trigger measurements.

Before VICP, bench instruments were controlled over GPIB (General Purpose Interface Bus), a parallel cable standard from the 1970s. VICP translates that same command language — IEEE 488.2 — into TCP/IP packets. Same protocol, new transport. The oscilloscope doesn't need to know the difference.

Who Uses It

VICP is specific to Teledyne LeCroy oscilloscopes. If port 1861 is open on a device, that device is almost certainly a LeCroy scope on a lab network. Engineers use it to automate test sequences, capture data remotely, and integrate instruments into larger measurement pipelines.

Teledyne LeCroy also developed VICP Passport, an NI-VISA compatible layer that lets standard instrument control software communicate with LeCroy scopes over the network without custom code.²

An open-source client library for parsing VICP packets is available on SourceForge.³

The Registered Port Range

Port 1861 sits in the registered port range (1024–49151). IANA maintains this range for services that have applied for an official assignment — not the universally-recognized well-known ports (0–1023), but not ephemeral or dynamic either. A registered port means some organization cared enough about this protocol to stake a permanent claim on the number.

Checking What's on This Port

If you see port 1861 listening on a machine and aren't sure why:

On Linux/macOS:

sudo lsof -i :1861
sudo ss -tlnp | grep 1861

On Windows:

netstat -ano | findstr :1861

Then cross-reference the process ID against your running processes. On a lab network, LeCroy scope traffic is expected. On a general-purpose machine, it would be unusual.

Security Considerations

VICP is a proprietary instrument control protocol — not designed with network security in mind. LeCroy scopes listening on port 1861 should be on isolated lab networks, not exposed to the broader Internet. An oscilloscope that accepts arbitrary remote commands from untrusted sources is a problem.

If you're administering a network and see port 1861 open, confirm it's a known LeCroy instrument and that it's appropriately segmented.