CompuTools Teleplex Blog

A change to the Windows TCP/IP stack (actually, a complete rewrite) breaks some IPv4 Multicast application including TPXMDIView on Windows Vista and Windows 2008.

The default address used by Teleplex and TPXMDIView is “225.0.0.1″.  Apparently, the system ignores multicast packets where the lowest part of the address is “1″.  In fact, you can’t even see the packets with Wireshark (Ethereal).

However, if you change the multicast address to any other valid, non-reserved multicast address, it works.

We have changed the default multicast address in Teleplex and TPXMDIView to “225.0.0.225″.  However, if you want to use TPXMDIView in an existing installation on one or more Vista systems, you must change the current settings in Teleplex and all of the client machines that run TPXMDIView so that they match.  Also, if you have a router for a multi-subnet LAN and must pass TPXMDIData between subnets, you must enable Multicast pass-through fon the router or the new address.

Why this is so is still under investigation.

Many of our customers use Microsoft SQL Server, and recently, we have been using Microsoft SQL Server 2005 Express at sites where the advanced features of the full product are not required.  The Express edition is great for IVR systems, small call centers, and for small web sites, but it also has some limitations including (1) it will never use more than 1GB of memory, and (2) the maximum database size is 4GB.  (The maximum database size was increased to 10GB in SQL Server Express 2008 R2.)

Generally speaking, these limitations have no effect on us because the main thing that we do is save call detail and agent activity data.  (The database isn’t used for processing millions of online orders, so we don’t need petabyte databases with hyper-performance.)  However, the question “What happens if the database fills up?” sometimes arises,  and the related question “How big is my database now?”

The answer to the first question is:

1. Teleplex will keep running, and will write the data to a text file (provided that the disk isn’t actually full), and
2. You will start getting supervisory Alerts, along with error messages like this: 

The portion shown in yellow is from SQL Server, and the “NativeError” is the actual SQL Server error code.

The answer to the second question can be found by one of the following methods:
 

1. In Microsoft SQL Server Management Studio (“SSMS”) right-click on the database in question to reveal its properties.  On the “General” property page you can see the “Size” and the “Space Available”.  The Size is the allocated size on disk, which is not necessarily how much space is actually in use inside the database.  Space Available indicates the amount of free space within the allocated space, not within the maximum space allowed.  Therefore, these numbers do not necessarily show whether you have hit the 4GB limit or not because the allocated size might show 4GB, but there might actually be unused space within that 4GB.  (Of course, you are probably reading this article because you are running out of space.)Furthermore, SSMS seems to display the sum of sizes of the “.MDF” (Master Data File) and “.LDF” (transaction log) files (which is confusing), so the magic number you are really looking for is a total Size of around 5GB.
    
2. Look directly at the size of “.MDF” file.  With a default installation, data files will be in “C:\Program Files\Micrsoft SQL Server\MSSQL.1\MSSQL\Data”.  If the “.MDF” file is around 4GB, you are probably near the limit.

Note that in the SSMS Database Properties “Files” page, you can also see under the “Autogrowth” column how the database is configured to grow.  The default settings allows a database to grow automatically to an unlimited size (although the Express server, as mentioned, has a maximum limit of 4GB).  You may want to confirm that someone didn’t actually limit the size.  (If so, you can change the configuration by clicking on the button in the Autogrowth column.)
 

When the database appears to be full, you should do the following:

• Check the obvious: Are you actually almost out of disk space?  If so, delete some unnecessary files.  You can probably quickly free up some disk space by deleting the contents of the Teleplex “Logs” subdirectory, deleting Internet Explorer temporary files, and by deleting files in any of your “temp” directories.
• If you still have plenty of disk space, check the database size as described above.  If you are nearing your configured limit, increase the limit.
• If, however, you have reached the 4GB limit of SQL Server Express, you have no choice but to delete some old data (or upgrade to the full version of SQL Server).  You easily delete old data from the “Manage Database” screen in Teleplex, and probably the best place to start is with the Call Log, which will get you back to a normal running state in short order.

Of course you should always do the following anway:

• Make regular backups.
• Monitor your disk space.
• Delete old data.
• If you are low on disk space, use SMSS to shrink the database (or use the DBCC SHRINKDATABASE command).  You might also want to consider moving the database to a larger drive or partition.

What do the error messages “Unable to accept call in the current state” and “Unable to answer call in the current state” mean?

There are three computers involved:  The PSTN-side switch (i.e., the telephone company), the CPU on the Dialogic ISDN board inside the Teleplex server, and the CPU running Teleplex.

A simplified typical inbound call flow is shown below.

The tricky part, and the source of the error occurs in the middle column.  Suppose, for example, that the caller hangs up sometime during steps (3) or (4).  (This really means, because everything is so fast, that the caller dialed the number and immediately hung up-even before the first ring.)  The board knows that the caller wants to disconnect, and may have even informed the Dialogic driver.  However, Teleplex is still waiting, in parallel, for the Accept function to return.  So when the Accept message arrives at the board from the application in Step (5), the board says “No silly!!  Unable to accept call in the current state”.  (Sorry.  How was I to know?)

On the Teleplex-side, the function to Accept the call returns an error code, and Teleplex displays an error message.

You can ignore these “error” messages, which are not really errors at all.

Finally, we changed Teleplex from Version 3.51.0.8 so it will display an informational rather than an error for this case.