>>I have many simulators and some utilities that send and receive data via a serial port. this works fine in windows xp but on windows 7 the utilities never receive any data through the serial port. If I switch to the modem serial port and pass ATZ, it returns with an OK immediately so I know it is working. If I put any of the simulators (that basically continuously send data through the port) on com1 and then put another utility/simulator that reads data on another com port (or on another machine on a comm port connected via a cable) , the one receiving never fires the oncomm event of the mscomm control.
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>>Any ideas what would prevent data from coming in a serial port?
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>What happens if the transmitter is Win7 and reciever is Win XP? Have you tried using Hyperterm on the receiver side and see if you see any differences?

Yes, I just tried that last night :o) It's strange. I get nothing in hyperterm either when the transmitter is Win 7 and the receiver is XP. I tried a couple of other "senders" as well (just to rule out any of my utilities). I tried Bernard Bout's scale emulator for sending data and still nothing on the receiver (win 7 or xp).

It's like everything going in and going out is blocked.

I tried creating a new comm form (slapping a new mscomm control on it) from scratch.

I've tried different cables - I have a regular serial with a gender changer adapter (I tried machine to machine with that last night), I have a regular cable with two female ends, and I tried the usb-->i/o cable. (in case it was my com1 port) using the virtual serial port. The results are nil with all of them.

However, I know the i/o port works because if I send data out the comm port to another system ( system that communicates via serial - not mine), it works fine.

Obviously something is up. I'm hoping that by starting fresh this morning I'll see the issue - either my mistake I've made along the way without realizing it, or something else.

Now, I don't have two xp machines to test with anymore :( I only have one xp machine left (everything else moved to win 7)... :(

Is anyone willing to test using a utility comm form I have and verify that data is going back and forth by running it twice - once against one port and the 2nd time against the 2nd port with a serial cable between the two? Or any other utility that just sends data (I tried using Bernard Bout's scale emulator) and my form receiving just to see if data goes back and forth?

Today I'm going to test hyperterm to hyperterm and all of the cables....

I think I've overlooked something or done something stupid. I just don't get it. Never had issues with a comm form like this before so it's bugging me!@!*#! :o)