modem - "cannot open port"

Posted on 1997-10-11
Last Modified: 2013-12-16
I'm installing Win95 on a new multimedia system with a network.  All is well, except I can't open the port to my modem.

At first I tried it with the internal modem that came with the pc.  Com2 was disabled at the bios, and Win95 correctly setup Com2 from the modem.  The settings all checked out.  When clicking on a modem connection I receive "dial up networking or another program is accessing your modem."  

Next, I uninstalled the internal modem and installed my old external modem to Com2, with Com2 enabled at the bios.  Same problem.

Then I changed Com2 to Com4, same problem.  

I've checked the register and ini files and don't see anything unusual.

I've lots of hours in this installation and setup, and I don't want to reinstall if I can avoid it.
Question by:gardanzo
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 2

Accepted Solution

magigraf earned 100 total points
ID: 1751052

Now assuming that you modem is set properly thsi documentation might be helpful if not I would wanna try few things if what I posting now does not help O.K.??
When you attempt to start a communications program, you may receive one of the following error messages:

•Error: port in use •OpenComm: Port already open


This behavior can occur if Rnaapp.exe is active in memory.


To work around this issue, follow these steps:

1.Press CTRL+ALT+DELETE to open the Close Program dialog box.

2.Click Rnaapp to select it, and then click End Task.

3.Start your communications program.


When you finish using a communications program and close the connection, Rnaapp.exe is still running and the port remains unavailable to non-TAPI programs.

Rnaapp.exe is left in memory to allow TAPI programs to open faster. Rnaapp.exe is eventually unloaded from memory (unless Dial-Up Networking Server is set to allow caller access), but it may take 10-15 minutes.
I would like to guide you an a few check points to verufy is

Expert Comment

ID: 1751053
if your modem is configured properly, keep me posted

Author Comment

ID: 1751054
I've got my old and new computers setup side by side.  In the old (works fine) one, when I click on the dial-up icon (picture of a telephone - makes a dial-up connection to my ISP) everything works fine.  Clicking on Ctrl-Alt-Del shows that rnaapp is not running.

Now, on the new computer, I do the same thing.  I check to see that rnaapp is not running, which it's not.  After clicking on the dial-up icon (setup exactly the same as on the old computer) I get this message: "The modem is being used by another Dial-up Networking connection or another program. Disconnect the other connection or close the program, and then try again."  I then check and note that rnaapp *is* now running.

So RNAAPP does appear to be the problem, but what do I do now? How do I prevent it from loading automatically?

Author Comment

ID: 1751055
Another symptom: If I go to control panel / modems / diagnostics, when I click on More Info I get " Couldn't open port."  All the settings of the port and modem appear correct.  After performing this task, RNAAPP is *not* running.

Author Comment

ID: 1751056
I got it!  I searched some of the PAQs here and found some other instances of the same problem.  Here was a suggestion from another expert:

Answer from wwillis...

Boot "safe mode command prompt only" and see if you can echo the com port the modem is on. If it is on com1 for instance you would type:
echo ata > com1
if the modem is responding correctly at that point it should go offhook and start making the handshaking noises. If it does type: echo ath > com1 which will hang it up. If that doesn't work you are having a problem with the modem that exists at the BIOS level (may try disabling the serial ports in CMOS setup if it is an internal modem) or a hardware failure with the modem itself. If it does work then you know for sure it's a Windows problem. At that point cd \windows\system and type: ren telephon.cp$ telephon.cpl and hit enter, then type: tapiini ...this will recreate the telephon.ini file in case for some reason it got corrupted. reboot back into Windows and test the modem. if it works, great, it was probably telephon.ini ...if not go to control panel. You should now have an icon for Telephony after renaming the .cpl file. Go into telephony and make sure Unimodem service provider is listed first. Sometimes some 16-bit service provider (old versions of AOL or Compuserve can hose this) will put itself first and that will stop all 32-bit communication (DUN and hyperterminal). If Unimodem isn't first there is an option there to change the order (can't remember precisely what the button says) and that should fix it. Good luck!


I followed Will's advice and received no response from the echo.  I went to the cmos and swapped com1 and com2 and all of their settings, so that my mouse would be com2 and modem com1.  After restarting, the mouse wasn't found, there was something wrong with com2 and its settings.

I switched them back and this time changed the irq setting for com2 from 3 to 9, and voila!  It fixed the problem.  Apparently there was something wrong with irq3 at the system board/bios level; this is why neither the external nor the internal modem worked on irq3.

Thanks for your help experts :-)

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

How to record audio from input sources to your PC – connected devices, connected preamp to record vinyl discs, streaming media, that play through your audio card: Vista, Windows 7, Windows 8, Windows 8.1 and Windows 10 – both 32 bit & 64.
The Windows functions GetTickCount and timeGetTime retrieve the number of milliseconds since the system was started. However, the value is stored in a DWORD, which means that it wraps around to zero every 49.7 days. This article shows how to solve t…
With the advent of Windows 10, Microsoft is pushing a Get Windows 10 icon into the notification area (system tray) of qualifying computers. There are many reasons for wanting to remove this icon. This two-part Experts Exchange video Micro Tutorial s…
Windows 10 is mostly good. However the one thing that annoys me is how many clicks you have to do to dial a VPN connection. You have to go to settings from the start menu, (2 clicks), Network and Internet (1 click), Click VPN (another click) then fi…

734 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question