Problem Description
If you try to make a remote desktop connection to a Windows Server 2012, 2012 R2, 2016, 2019 or Windows 7, 8, 8.1, 10 you can encounter the following Warning Message.
Warning Message
The number of connections to this computer is limited and all connections are in use right now. Try connecting later or contact your system administrator.
After this Warning Message, I logged on to the Server from the Console and opened the Task Manager to check if there is another Open Session on the Server but there were no other open Sessions.
I opened the SYSTEM Event Log first, to check if there is anything related to my Problem, but the only Problem I saw was a DNS Registration Problem. I decided to get an IP address from the DHCP Server automatically to eliminate this Problem and removed the Static IP from the Network Adapter which I used to connect to my Problematic Server.
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System Event Log
Log Name: System
Source: Microsoft-Windows-DNS-Client
Date: 5/23/2014 11:08:50 AM
Event ID: 8016
Task Category: (1028)
Level: Warning
Keywords:
User: NETWORK SERVICE
Computer: SCOM.kuskaya.local
Description:
The system failed to register host (A or AAAA) resource records (RRs) for network adapter
with settings:
Adapter Name : {554EA174-B18C-4E59-BE67-36FF2264E965}
Host Name : SCOM
Primary Domain Suffix : kuskaya.local
DNS server list : 192.168.1.1
Sent update to server : <?>
IP Address(es) : 192.168.1.5
The reason the system could not register these RRs was because the DNS server failed the update request. The most likely cause of this is that the authoritative DNS server required to process this update request has a lock in place on the zone, probably because a zone transfer is in progress.
You can manually retry DNS registration of the network adapter and its settings by typing 'ipconfig /registerdns' at the command prompt. If problems still persist, contact your DNS server or network systems administrator.
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Solution
I logged in to the Problematic Server via the Console, disabled and enabled the Network Adapter to get a new IP address from the DHCP Server and to clear the DNS cache on the Problematic Server.
I tried to make a Remote Desktop Session again and ….
BINGO !
I was able to successfully make an RDP Session to my Problematic Server. The Error Message “The number of connections to this computer is limited and all connections are in use right now. Try connecting later or contact your system administrator.” was definitely misleading.
The Root Cause of this Problem was in reality a Problem with the Problematic Server’s DNS Client Service as you can see from the Event Log above. Basically the DNS Client Service was not able to register itself on the DNS Server because of an unknown reason. Releasing the IP Address and clearing the Problematic Server’s DNS Cache by disabling and enabling the Network Adapter fixed the Problem. Please check your Problematic Server’s or Pc’s “SYSTEM Event Log” too. It will definitely tell you something about the reason of the Problem.
Today we are in 2020 and it’s 6 years ago since I wrote this article and I haven’t experienced this problem again on the same or another Server.
Good luck !