Invalid Connection Passwords when connecting to groups

Problem: you create a classroom group and set a password on that group on one day and the next day, when you try to connect to that group, you are unable to connect to some of those machines, and you get an "Invalid Connection Password" message.

This typically happens when your network DHCP/DNS servers are not properly synched.  A word of explanation about how groups work will help clarify how this occurs.

When you create a classroom group, AB Tutor Control will store the machine name only of each computer in that group - it will NOT store the IP address unless you specifically hard code it (e.g when you add a new computer in a group, just enter the IP address rather than the computer name).  In the example below, two separate groups have been created, Group A and Group B each containing just 3 computers all with different names.
 




Each group has been set a different Group password, pw1234 and pw5678.  When the AB Tutor Control program launches and tries to connect to the computers in Group A, the first thing it does is go to the DNS Server (which is responsible for storing the IP addresses of all computers on a network) to ask for the IP addresses of the computers to which it needs to connect. In our example, it asks the DNS for the IP address of the computer whose name is A-Comp01.  The DNS returns the IP address of 192.168.1.11.

If the network is set up and running fine, then this would be the correct IP address for computer A-Comp01 and the connection would be made.  However, if the DNS Server is out of synch with the DHCP (which is responsible for dynamically allocating IP addresses as computers switch on and off) then this IP address would be wrong.  In this example, the DHCP has recently changed the IP address allocated to computer A-Comp01 - it is now 192.168.1.15.  So when AB Tutor Control attempts to connect to IP address 192.168.1.11 (the out-of-date IP address stored in the DNS), the network tries to connect instead to B-Comp02 using password pw1234.  Because this is a computer in a different group, with a different password, then the connection will fail, and an invalid connection password will be returned. 

Solution

Please read this knowledgebase article for information on how to solve this problem.  Sometimes ABTC seems to allocate names to machines at random.