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ID: AR11L00823
Applies to: NX Software
Added on: 2014-11-07
Last update: 2019-02-01
How to solve port conflicts with other applications

A port conflict occurs when a program is already using or requires any of the ports adopted by NoMachine services.  

The same port conflict can have two different symptoms depending  on which application has been started firstly, NoMachine or another program.  In the first case, the error message should be reported by NoMachine, in the second case by the other application.

The most common cases of possible port conflicts are:

1. The Network Server (nxd) cannot be started, connection timeout when using the NX protocol

2. The SSH server (nxsshd) cannot be started, connection timeout when using the SSH protocol (for Windows only)

3. The HTTP Server (nxhtd) cannot be started, connection timeout for web sessions

4. USB forwarding is not available

5. Conflicts on port 700*

6. Conflicts on port 1100*

1. The Network Server (nxd) cannot be started, connection timeout when using the NX protocol.

The nxd service listens by default on port 4000.  

To solve the conflict you can change the default port from the NoMachine User Interface in the Server preferences → Network services panel or by editing the server configuration file (namely server.cfg), uncommenting and setting a different value for the NXPort key.

For example:
NXPort 4002

2. The SSH server cannot be started, connection timeout when using the SSH protocol.

The nxsshd service listen by default on port 4022. This service is available only for Windows, on the other platform NoMachine relies on the system SSH server.

To solve the conflict you can change the default port from the NoMachine User Interface in the Server preferences → Network services GUI or by editing the server configuration file (namely server.cfg), uncommenting and setting a different value for the SSHDPort  key. 

For example: SSHDPort 4020

3. The HTTP Server (nxhtd) cannot be started, connection timeout for web sessions

The nxhtd service listens by default on port 4080 for HTTP connections and on port 4443 for secure HTTP connections.

To solve the conflict you can change the default ports from the NoMachine User Interface in the Server preferences → Network services GUI or by editing the htd configuration file (namely htd.cfg) and set a suitable value for the following entries:
Listen 0.0.0.0:4080
Listen 0.0.0.0:4443 https

4. The USB service is not available.

The USB service uses ports 5473 and 5483 locally.  A new port is open for each USB device to be connected. This port is chosen in the 5040 + x range, where x is the first free port retrieved starting from number 5040.

These ports cannot be configured. A port conflict doesn't impact the functioning of the session, just connecting USB devices will be not possible.

5. Conflicts on port 700*.

The display service or agent, integrated in the nxnode process, listens on a port defined by DisplayBase  + 6000. NoMachine looks for the first free port by incrementing value of DisplayBase up to value of DisplayLimit. Both keys are in the server configuration file.

To solve the conflict, edit the server configuration file, uncomment and set a suitable value for the DisplayBase key. 
Please read also point 6.

It is known that a conflict on port 7001 can occur when using the WebLogic Server Administration Console.
Please read here for more details:

https://www.nomachine.com/AR11L00822

6. Conflicts on port 1100*

The display service uses also a port defined by DisplayBase  + 11000 .  NoMachine looks for the first free port by incrementing value of DisplayBase up to value of DisplayLimit. Both keys are in the server configuration file.

To solve the conflict, edit the server configuration file, uncomment and set a suitable value for the DisplayBase key. 
Please read also point 5.


Further references:

Default ports used by NoMachine 4 or later
https://www.nomachine.com/AR01L00770

Possible port conflict with WebLogic Server Administration Console
https://www.nomachine.com/AR11L00822