OverviewTactical Software redirectors support up to 4096 virtual COM ports in Windows 10, 8, 7, XP, 2016, 2012, 2008, 2003, and 2000 operating systems.Processor IssuesAn application will take more CPU cycles as it uses more COM ports, so it is important to be sure that there is enough processing power for the application to handle using all the simultaneous COM ports.On most PCs, there is a difference between the ability to have over 4000 ports redirected, and using all the ports at once. It is not hard to max out the CPU of a fast machine with 256 concurrent ports actively passing data, so the ability to use an even larger number of ports will depend greatly on the application behavior and the speed of the host machine.The application that is being used to open the COM ports and send data creates almost all of the stress on a system, while the overhead from Tactical Software redirectors is almost negligible. Therefore, if an application can use a certain number of real COM ports successfully, then the same results should be seen when using virtual COM ports.Unless a multi-port test is done with the same application that will be used in a real situation, it isn't possible to tell how many CPU cycles (or how much RAM) it will use, as the specific way that an application is written will determine the resources that it uses.Some applications take quite a large amount of CPU time per each COM port used, while other programs can transfer the same data using a different protocol with a fraction of the CPU usage.Networking IssuesA Windows machine will only be able to make 3975 active outbound TCP connections before running out of TCP port numbers. This alone prevents 4096 active COM port sessions, not even counting the fact that other programs will be making their own TCP connections.The TCP ports used for these connections are not available for re-use until several minutes have elapsed after a connection has been closed. An application which opens and closes COM ports frequently can easily cause the operating system to run out of TCP ports.There is a registry setting that can be changed to raise the amount of TCP ports available to Windows:HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersOn the Edit menu, click Add Value, and then add the following registry value:
Value Name: MaxUserPort
Data Type: REG_DWORD
Value: Default: 0x1388 (5000 decimal, (which gives 3975 available ports)); Max: 65534(decimal)Finding the optimum value for this registry setting will require some experimentation as it is dependent on the serial application that is used and other TCP/IP based programs on the same PC.Additional ConsiderationsTactical Software recommends testing with the same COM port count as needed in the production deployment to ensure the PC has enough RAM and processor cycles to run smoothly.
After testing the application successfully with hundreds (or thousands) of real COM ports to be sure that it will not be short CPU cycles or system RAM, keep in mind that the available TCP port range mentioned above must be set high enough so that Windows will not run out of usable TCP port numbers.