Verify an instrument LAN connection with Telnet

The fastest possible sanity check: ping the instrument, open a Telnet session to the SCPI port, and type *IDN? by hand.

5 min readIncludes code

When remote control misbehaves, test the layers in order: cable → IP → SCPI. Telnet gives you a live keyboard session straight into the instrument's SCPI parser, so you can prove the network path with zero code.

Step 1 — Ping the instrument

bash

ping 192.168.1.121

What you should see

Reply from 192.168.1.121: bytes=32 time=1ms TTL=64

No reply? Fix this first: check the cable/link LEDs, confirm the instrument's IP settings (DHCP vs static) in its LAN/IO menu, and make sure PC and instrument share the same subnet.

Step 2 — Check which port your model actually offers

Do this before you blame the network. The Telnet service on port 5024 is not universal, and it is not even the common case for every product type. Every Siglent power supply and the DC electronic load offer the raw SCPI socket on 5024's neighbour, port 5025, and no Telnet service at all. Connecting to 5024 on an SPD3303X will fail, and that failure tells you nothing about the instrument.

Services	Models
Telnet 5024 and socket 5025	SDS5000X, SDS2000X Plus, SDS2000X-E, SDS1000X-E, SDS1104X-U, SDG6000X, SDG2000X, SDG1000X, SSA3000X, SSA3000X Plus, SSA3000X-R, SVA1000X, SDM3045X, SDM3055, SDM3065X, SSG3000X, SSG5000X, SNA5000A
Socket 5025 only — no Telnet	SPD3303X, SPD3303X-E, SPD1000X, SPS5000X, SDL1000X
Neither — use VXI-11 or USB	SDS2000X, SDS1000X, SDS1000CML+, SDS1000DL+, SDG800, SPD3303C, SHS800, SHS1000

Which services a given model offers is published by Siglent in Instrument Socket and Telnet Port Information. Check it before assuming — the pattern is not uniform across the range, and the power supplies in particular offer the socket but not Telnet.

Step 3 — Open a session on the right port

Windows: enable the Telnet client once via Turn Windows features on or off, or use PuTTY in Raw mode (see the related note). Then, depending on which row your instrument is in:

bash

# Models with the Telnet service - interactive, echoes a banner and a prompt
telnet 192.168.1.121 5024

# Models with the raw SCPI socket - no banner, no echo, but it answers
telnet 192.168.1.205 5025

Port 5024 is an interactive Telnet service: it prints a welcome banner and a prompt, and echoes what you type. Port 5025 is a raw socket — it prints nothing, echoes nothing, and looks dead until you press Enter on a query. A silent window on 5025 is normal, not a fault. PuTTY in Raw mode with local echo on is more comfortable for this.

Step 4 — Type a query

scpi

*IDN?

What you should see

Siglent Technologies,SPD3303X,SPD3XIDD5R0001,1.01.01.02.05

A full identification string proves cabling, IP configuration and the SCPI service in one shot. If this works but your program doesn't, the problem is in your code or VISA layer — not the network.

Instruments used in this note

Siglent LAN instruments

Telnet 5024 where supported; raw SCPI 5025 more widely

View

Related application notes

Test SCPI socket communications with PuTTY Verify a remote connection with NI-MAX Open-socket LAN control with Python (port 5025)

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