Find Out If A Firewall Is Blocking Your Remote Control Software

If you ever tried to help a user at another location, you have appreciated the usefulness of remote control software. But, you might not be able to connect to it after installation. When that happens, you must determine whether the user's firewall is causing the problem, or if it is some other issue with the user's computer. Both computers should be on the same site for you to use these tips; If your user's computer is offsite, this procedure will be useless. The computer with the issue (Computer 1) should have an operating system that includes the Telnet utility, such as Windows XP. You will also need its IP address, or its DNS name. Computer 2 should have an operating system that includes the Telnet utility. There must be a reliable working network connection between the two.

Step1

Find out the IP port number that your remote control software uses. You can get this information from your remote software settings in your user computer, its documentation or its technical support. Here are the more common IP port numbers: 3389 - Microsoft's Remote Desktop connection Protocol (RDP) 5631 - Symantec's PC Anywhere (default; it can be changed) 5900 - Open Source Forge's VNC and its derivatives (ditto) 4899 - Famatech's Remote Administrator (ditto)

Step2

Click "Start." A toolbar or a window will come up.

Step3

Click "Run." A window will come up with a place to type a command or other text.

Step4

Click on the rectangle (or text field) and type this command: cmd Press "Enter," or click "OK" A (usually) black window with a blinking cursor will come up. This window has the title Command Prompt.

Step5

Click the title bar or anywhere else inside the window, to select it. You should be able to type commands into it.

Step6

In the Command Prompt window, type this command where the (IP address) is replaced by Computer 1's IP address or DNS name: start telnet (IP address) (TCP port number) Start allows the command you type next to come up in a separate window. Telnet is a (text) terminal emulation program that uses TCP/IP instead of a serial cable to connect to computers. (IP address) is replaced by your 4-number set, also known as the dotted quad. It is the Internet equivalent of a phone number. It can also be replaced by your DNS name. The last one is your TCP port number. This you will replace with your particular port number as applicable. Examples: start telnet 10.120.201.18 3389 or: start telnet mail.yourfriend.local 4899

Step7

These steps only test if your TCP port number is open on Computer 1 to the outside world. You may still have an issue with the remote control software that prevents you from connecting. If everything else is in order, rebooting Computer 1 usually takes care of the issue, at least for a while.

Test Your Rmote Control Software in Computer 1 (steps are very similar to Section 1)

Step1

On Computer 1, click "Start." A toolbar or window will come up.

Step2

Click Run. A window will come up with a place to type a command or other text.

Step3

Click on the rectangle and type this command: cmd Press "Enter," or click "OK." A (usually) black window will come up. In it it will have a blinking cursor. This window has the title Command Prompt.

Step4

Type this command, and press "ENTER:" IPCONFIG As a response, you will get text such as this: Windows IP Configuration Ethernet adapter Wireless Network Connection: Connection-specific DNS Suffix . : IP Address. . . . . . . . . . . . : ###.###.###.### Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : ###.###.###.###

Step5

Make a note of the set of four numbers (or the "dotted quad") in the IP Address line. Then type the command: start telnet (your IP Address) (your TCP port number) Continue to our next step.

Step6

A second window will come up. The text Connecting to (blah blah blah) ... may show up. One of these things may happen: 1- The text above lingers for more than half a second or so, and then the screen closes, so you are back to the previous window. This means Computer 1 has nothing listening on that particular port. Either your remote control software is not active, it cannot become active for some reason, or else it is listening in another TCP port. You can now contact your remote control software technical support and have them help you figure out what the problem is. 2- The screen is blank except for a cursor. This means Computer 1 has some software listening on that TCP port. Hopefully, it is your remote control software who is listening. You can press ENTER or the letter q, and usually this window will close. If your results on Section 1 were that no connection can be made on this same TCP port, then there is a firewall or other software on Computer 1 blocking this port for inbound connections. You will need to look into Computer 1 to see if Windows Firewall or a third-party firewall software is causing this issue. Common culprits are Windows Firewall, Norton Security, or ZoneAlarm. Instead of disabling the firewall, it is better to tell it to accept inbound connections at that port. 3.- In rare instances, the second window opens and closes almost immediately, and you are back to the first one. In this case, the port is actively refusing the connection. Either your remote control software is acting up, or some other software is listening to that TCP port. You will need to verify that your TCP port number is indeed correct. NOTES: These steps only test if your TCP port number is open on Computer 1. You may still have an issue with the remote control software itself that prevents you from connecting. If everything else is in order (authentication, etc), rebooting Computer 1 usually takes care of the issue, at least for a while. Reinstallation may be also an option. Otherwise, you will need to contact your remote control software tech support.