Common Causes for Linkus Failure - Failed to Connect to Server

  • Applicability
  • Common Causes
    • Incorrect Port Forwarding
    • Linkus Server hasn't been enabled
    • IPv6 network
  • Log Capture



  • PBX version: or higher
  • Linkus server version: 2.6.10 higher



Commonly, you would get the error prompt Failed to Connect to Server (1) 


If you meet Failed to Connect to Server (3), you refer to this article: Linkus Login Failed through LCS - Error Code 3


Common Causes

  1. Incorrect Port Forwarding
  2. Linkus Server hasn't been enabled
  3. Login via IPv6 network



Let's what are the exact causes and the solutions:

1. Incorrect Port Forwarding

Make sure you have forwarded ports 8111(UDP and TCP), 5060 UDP, 10000-12000 UDP on your router for

the PBX (Especially port 8111). Please refer this article to configure the port mapping for Linkus:

You can also use this web tool to check if your port has been forwarded.

Enter your public IP of the PBX uses, and the port you want to check.

For example, it shows 8111 is not forwarded.


If you don't want to do port forwarding, you could try our LCS service. Enable Linkus Cloud Service(LCS)

on the Linkus Server. LCS uses the tunnel to transmit data it does not needs to set port forwarding on the

router and more secure. See how to use LCS


2.  Linkus Server hasn't been enabled

Make sure your Linkus server service has been enabled.


3. IPv6 network

Linkus client has already compatible with lots of IPv6 networks. But the IPv6 is complicated, in order to

exclude the network issue. Please try to change your Linkus client to the IPv4 network and test.

For example: 

1. Change your SIM card network to IPv4 if you data network to login Linkus.




Log Capture

If the problem still exists, please try to capture and post us the logs follow the below step when you replicate the issue.

1. Enable debug and sip debug on the PBX(no need to put any IP to sip debug


2. Log in the Linkus and click 'login' to make the problem happens again

3. Download the System log from the PBX


4. Get log from Linkus client, please refer to this link to get the Linkus client log



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