USB connection problems: "port already open"

[anamaria.mica]

Hello,
I am trying to write an application to send sms from a PC via a
phone/
gsm modem connected to that pc but i sometimes get a problem when i
try to get the connection with the modem.

When i connect the usb cable to the port and go to either Control
Pannel -> Phone and Modem Options, select the gsm modem and try to
query it or when i open Hyperterminal and try to make a new
connection
to the COM port i get a message: "Port already opened".


This means another application openes a connection with my port and
keeps it opened. the problem gets solved if i restart the computer
(sometimes i have to restart it several times to be able to query the
modem)


How can i detect what application openes a communication with the
port? and how can i prevent this to hapen? and why does it happen?


I have run these tests on different pc's (both Windows XP and Windows
2000) and it hapened on each of
them. but not always.


I would highly appreciate any sugestions,


Thank you,


Anamaria
(e-mail address removed)

 

[Uwe Sieber]

Hello,
I am trying to write an application to send sms from a PC via a
phone/
gsm modem connected to that pc but i sometimes get a problem when i
try to get the connection with the modem.

When i connect the usb cable to the port and go to either Control
Pannel -> Phone and Modem Options, select the gsm modem and try to
query it or when i open Hyperterminal and try to make a new
connection
to the COM port i get a message: "Port already opened".


This means another application openes a connection with my port and
keeps it opened. the problem gets solved if i restart the computer
(sometimes i have to restart it several times to be able to query the
modem)


How can i detect what application openes a communication with the
port? and how can i prevent this to hapen? and why does it happen?

Get SysInternals ProcessExplorer:
http://www.microsoft.com/technet/sysinternals/utilities/ProcessExplorer.html

Start it, press Ctrg+F to search for handles, enter serial0 which
usually is the internal name of COM1.


Uwe