There are several scenarios when DS-Client may fail to start with an error mentioning ports: 

1. Port 4403 is being used by a Windows service or another application.

In order to operate, the DS-Client needs to open port 4403 for the TCP/UDP protocols on the machine where it is installed. If it fails, the DS-Client service will stop and will record the following error in the Windows Application Log: "Failed to open ports (ds-user,TCP)." DS-Client may fail to start on some Windows Operating Systems because of a port conflict between the DS-Client and some Microsoft services like WMI. A workaround from Microsoft to resolve the port conflicts is described below: 

  • a. Run "RegEdit". 
  • b. Browse to "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\TCPIP\Parameters" 
  • c. Double click the key named "ReservedPorts", and add "4403-4403" 
  • d. Make sure that the key value ends with one empty line by hitting the "Enter" key. 
  • e. Click the "OK" button to save the Registry changes. 
  • f. Restart Windows and the port conflict should not occur. 

2. The 'services' file in c:\Windows\system32\drivers\etc is missing the following lines:

ds-user 4403/tcp #DS-Client administration port 

ds-user 4403/udp #DS-Client administration port 

ds-srvr 4401/tcp #DS-System operating port 

3. Port 4403 is blocked by a firewall.

4. HKLM\System\CurrentControlSet\Services\TCPIP\Parameters\DatabasePath registry key is REG_SZ instead of REG_EXPAND_SZ

MSN messenger 7.0/7.5 changed this registry key, so the path to the service file is not properly loaded. After changing the type of the registry key, DS-Client will run however if you run MSN messenger 7.0/7.5 again, it will change the key again. So please don't run MSN messenger 7.0/7.5 on the DS-Client computer.