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Firewalls and Proxy Servers with PC Access® for Windows

Quick Contents

Introduction

PC Access for Windows is an enhanced emulation program that allows you to remotely access the MLS system. If your MLS office provides Internet access to the MLS system, you should set up PC Access to connect using TCP-Telnet. For more information, see: Connection Method group.

Many local area networks (LANs) and end-users may use a firewall or proxy server on their Internet connection. You may use a firewall or proxy server to prevent hackers from accessing your system. The firewall or proxy server may also prevent you from using the TCP-Telnet connection method in PC Access for Windows to connections to your MLS system.

PC Access TCP-Telnet connections rely on the Windows 16-bit TCP/IP-Winsock driver (C:\WINDOWS\WINSOCK.DLL) for its Telnet sessions. Windows TCP/IP-Winsock Telnet sessions use Port 23 or Port 24. If the firewall or proxy server does one or more of the following:

  • blocks ports 23 or 24
  • does not properly route the Windows 16-bit TCP/IP-Winsock calls
  • logs into the firewall or proxy server before allowing telnet access to the Internet
all PC Access TCP-Telnet sessions will fail.

Solution

You can use PC Access for Windows and your firewall or proxy server when one of the following conditions are true:
  • your firewall or proxy server correctly routes the Windows 16-bit TCP/IP-Winsock calls through the firewall or proxy server's SOCKS driver.
  • your firewall or proxy server allows inbound and outbound traffic through the Telnet ports 23 or 24
  • you provide direct telnet connections through the firewall or proxy server where the PC Access TCP-Telnet sessions will connect to the MLS system via the Internet.
MFM has a list of settings for several firewalls and proxy servers. You can use these settings to configure your firewall or proxy server to allow PC Access to use a TCP-Telnet session to connect to your MLS. For more information, see: Known Firewalls and Proxy Servers.
  • Note: MFM Technical Support does not support or provide assistance with configuring any firewall or proxy servers. If you are unsure about how to configure or work with your firewall or proxy server, contact technical support for your firewall or proxy server software.

Known Firewalls and Proxy Servers

The firewalls and proxy servers in the following topics may cause problems with PC Access for Windows TCP-Telnet connections. If you are using one of the firewalls or proxy servers in the following topics, you may find a possible solution(s) to your problem.
  • Note: MFM Technical Support does not support or provide assistance with configuring any firewall or proxy servers. If you are unsure about how to configure or work with your firewall or proxy server, contact technical support for your firewall or proxy server software.

Microsoft ISA Server

The Microsoft Internet Security and Acceleration (ISA) Server does not support Windows 16-bit TCP/IP-Winsock calls in Windows 95, Windows 98/98SE, and Windows Millennium Edition. However, Microsoft does provide a workaround for this limitation. Microsoft's ISA Server does support Windows 16-bit TCP/IP-Winsock calls in Microsoft Windows NT 4.0 and Windows 2000 only. For more information, see this article in the Microsoft Knowledge Base:

Deerfield.com Wingate Proxy

You will need to contact Deerfield Wingate Support to obtain instructions on configuring Wingate to allow PC Access for Windows TCP-Telnet connections. Deerfield Technical Support contacted MFM Technical Support about the TCP-Telnet connection problem. Deerfield does have a solution available for its customers. Deerfield did not provide MFM Technical Support the solution. Instead, they suggested customers contact their technical support. You can visit the Deerfield Web site:

Microsoft Proxy 2.0

Microsoft Proxy 2.0 with or without the Proxy Server Pack installed will prevent successful PC Access for Windows TCP-Telnet connections. You will need to contact Microsoft Proxy Support for a solution to this problem. MFM has never received any information on the solution that Microsoft provided.
  • Note: to our knowledge, Microsoft Proxy 1.0 works with PC Access for Windows TCP-Telnet sessions.

Ositis WinProxy 2.1

For instructions on how to set up Ositis WinProxy 2.1 to allow successful PC Access for Windows TCP-Telnet connections, you will need to visit the Ositis Web site.

On the Ositis Web site, you will find a solution posted in their Knowledge Base on how to configure WinProxy 2.1 for direct Telnet connections. Here is the hyperlink to their Knowledge Base article:

If the above URL does not work, you can search their site for article reference number: 990301-000020.

Based on information on the Ositis Web site, WinProxy 3.0 does not have this limitation. You also do not need to configure WinProxy 3.0 to allow direct Telnet connections through the proxy server.

Zone Alarm and Zone Alarm Pro

To allow successful PC Access for Windows TCP-Telnet sessions in Zone Labs ZoneAlarm or ZoneAlarm Pro, you need to allow PCAWIN.EXE or PC Access for Windows to have Internet access.

Sygate Personal Firewall

MFM Technical Support has received reports from some PC Access for Windows TCP-Telnet users who use the Sygate Personal Firewall. These users report that they cannot telnet to the MLS system via the Internet using PC Access for Windows 4.20 or 4.30.

The PC Access for Windows TCP-Telnet session will show a 609 error when a firewall or proxy server blocks access to the Telnet ports in the Windows TCP/IP-Winsock driver. The Windows TCP/IP-Winsock Telnet ports are either 23 or 24.

To connect to the MLS system via the Internet and PC Access for Windows, you will need to do one of the following:

  • configure the Sygate Personal Firewall to allow Telnet sessions (if this option is available).
  • temporary disable Sygate Personal Firewall.
However, disabling Sygate Personal Firewall does not guarantee that PC Access TCP-Telnet sessions will be successful. This firewall program runs other blocking programs in the background.

Windows XP Internet Connection Firewall

Windows XP has an integrated Internet Connection Firewall. This firewall does not conflict with PC Access for Windows 4.20 and 4.30 TCP-Telnet sessions.

However, if you use a third-party firewall or proxy server program and/or use an ICMP checking program to keep your connection alive with the Windows XP Internet Connection Firewall enabled, you will probably experience Internet connection problems due to a high volume of packet loss.

If the packet loss problem relates directly to the Windows XP Internet Connection Firewall, you will need to do the following in Windows XP to eliminate the packet loss:

  1. In Windows XP click Start | Control Panel | Network Connections.
  2. In the Network Connections window right-click on the Local Area Connection icon and click Properties.
  3. In the Local Area Connection Properties window click on the Advanced tab. Select Protect my computer and network by limiting or preventing access to this computer from the Internet to enable Windows XP firewall.
  4. Click the Settings button (towards the bottom of the window) to open the Advanced Settings window. Click on the ICMP tab and select Allow incoming echo request.
  5. Click OK | OK to return to the Network Connections window and close it.

Microsoft Knowledge Base References:

Troubleshooting Guide Links

[Troubleshooting Home] [Installing PC Access] [User Authorization] [Setting up PC Access] [E-mail and Internet Problems] [Running PC Access] [Calling the MLS] [Logging in to the MLS] [Communicating with the MLS] [Printing] [Third-party Software Problems] [Miscellaneous]
 

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