Failed to start server on port 1234

Topics: LM Studio

While playing with local LLMs (Large Language Models) in LM Studio on Windows, I got a following error while trying to start LLM server:

{ "cause": "{\"code\":\"EACCES\",\"errno\":-4092,\"syscall\":\"listen\",\"address\":\"0.0.0.0\",\"port\":1234}", "data": { "memory": { "ram_capacity": "33.95 GB", "ram_unused": "13.21 GB" }, "gpu": { "type": "NvidiaCuda", "vram_recommended_capacity": "8.59 GB", "vram_unused": "7.48 GB" }, "os": { "platform": "win32", "version": "10.0.22631", "supports_avx2": true }, "app": { "version": "0.2.10", "downloadsDir": "C:\\Users\\user\\.cache\\lm-studio\\models" }, "model": {} }, "title": "Failed to start server on port 1234" }

The solution was to restart WinNAT service in the following way:

• Open CMD (command line) as admin and run:
  1. net stop winnat
  2. net start winnat

Source

What is WinNAT?

Windows NAT (WinNAT) is a network address translation (NAT) service designed to provide connectivity between virtual machines (VMs) and the external network in a Hyper-V environment. It acts as a router and enables VMs to access external resources using a NAT IP address.