This page is a part of VPortPro online Help Manual.
VPortPro-client with Com Port Control by Labtam.
VPortPro makes serial (RS232) data from your PC available on TCP/IP-based networks and makes TCP/IP data available on virtual serial ports of your PC. Visit Home of VPortPro for more information.

Using ComSetup

You can start ComSetup by clicking on the ComSetup item in the VPortPro Programs' folder (i.e., from the Start/Programs/VPortPro menu):

The Communication Setup / Windows Sockets dialog box will appear on your display:

By clicking OK, any new settings you make to the Communication Setup dialog box will be saved in the xwp.ini file (by default) and the dialog will be closed. (See also section Running ComSetup with command line parameters below.)

You can cancel any changes you have made to the dialog box and close it by pressing Cancel.

There are some additional settings you can specify to customize ComSetup. They are described in section The "[NETWORK]" Section of the ini-file below.

The following input fields are available:

The Hosts File

This field is used to specify a location of the hosts file. You must enter the hosts file that is used by MS Windows (C:\WinNT\System32\drivers\etc\hosts for MS Windows NT4/2000/XP and C:\Windows\hosts for MS Windows 9x/ME).

The hosts file is a list of remote computers in the standard format (IP-address hostname aliases). The contents of the hosts file will be used by other programs of the package when you want to select a host to connect to from the host list box.

WinSock DLL

This field specifies the DLL that provides Windows Sockets Interface to existing TCP/IP stack. By default, wsock32.dll of the Microsoft Windows' TCP/IP will be used. You can specify to use any other TCP/IP stack by entering its 32-bit Windows Sockets Interface DLL.

Auto-start XwpPeg Package Watcher

With this check box enabled, the XwpPeg utility is started automatically with starting any package's application. Otherwise, you can launch XwpPeg manually.

Enable TCP/IP KeepAlive mode

This check box specifies the package's applications to use the TCP/IP feature, KeepAlive, when communicating with remote computers over your network. When enabled, this prevents your connection from interrupting by a remote computer when your PC does not send messages to it for a long time.

Enable Logotype

This check box toggles displaying the Logotype image each time the package's application starts up.

Disable Log Output

When selected, this check box prevents any program of the package from writing log information to the ".out" and ".ini" files.


This button lets you choose the network transport.


This button will initialize all these parameters to their default values.

The If non-single IP address Box

If your PC has more than one IP address (i.e. 'multi-home' PC with non-single TCP/IP stack, e.g. for Ethernet + modem), then you should specify a mode for choosing one of them.

Always Use the First IP address
Always Use the Last IP address

These modes allow VPortPro's programs to automatically choose the local IP address.

Ask to Choose

You can set up this mode to specify that you will choose the address in the dialog box brought up by the programs. The default mode is Ask to Choose.

The TCP/IP Info Box


When you click on this button, ComSetup will search for available TCP/IP information and, if found, display in the info field the IP address and name of your PC according to mode settings.

Create 'sp_ghbn.out' Info file

If this check box is enabled, then all information found will be stored in the file. This allows you to check accessibility and obtain description of the TCP/IP stack used.

The XwpPeg Utility

XwpPeg is a program designed to check the state of the package license accounts. XwpPeg informs users about exceeding the allocated license accounts over the specified limit. If all users of the same package have XwpPeg running simultaneously with running any package's application (and terminate after completion of the last one) then all those users will have true information about the number of concurrent package users who use package license accounts (i.e. the allocated accounts).

You can launch XwpPeg either automatically or manually. With the Auto-start XwpPeg Package Watcher check box enabled, XwpPeg is started automatically with starting any package's application.

Users can independently launch XwpPeg (before starting any package's application) to check/allocate one license account in advance. If the user starts XwpPeg manually then he/she must also manually terminate it to free the package license account allocated. Since XwpPeg is only informational, users can freely terminate it at any time; however they cannot automatically check the current number of concurrent users of the same package in that case.

You can start XwpPeg by clicking on the XwpPeg item in the VPortPro Programs' folder (i.e., from the Start/Programs/VPortPro menu):

If you do not want to display the XwpPeg window, you should set to zero the value of the WorkMonitor variable in the "[XWPWATCH]" section of your xwp.ini file (e.g., WorkMonitor=0). To display the window, set the value to unit.

If you click on the Settings button, the following dialog box appears:

When you have made desirable settings, press OK.

The TCP/IP Retransmission Timeout Parameters

TCP starts a retransmission timer when each outbound segment is handed down to IP. If no acknowledgment has been received for the data in a given segment before the timer expires, then the segment is retransmitted, up to the TcpMaxDataRetransmissions times. The default value for this parameter is 5.

When a TCP connection is established, the retransmission timer is initialized to three seconds; however, it is adjusted on the fly to match the characteristics of the connection using Smoothed Round Trip Time (SRTT) calculations (as described in RFC793). The timer for a given segment is doubled after each retransmission of that segment. Using this algorithm, TCP tunes itself to the normal delay of a connection. TCP connections over high-delay links will take much longer to time out than those over low-delay links.

By default, after the retransmission timer hits 240 seconds, it uses that value for retransmission of any segment that needs to be retransmitted. This can be a cause of long delays for a client to time out on a slow link.

MS Windows NT4/2000 provide a mechanism to control the initial retransmit time, and then the retransmit time is self-tuning. The following is based on the Microsoft Knowledge Base and Microsoft MSDN Library.

To change the initial retransmit timeout parameters, you can modify the following values in the following registry key:


Value Name: InitialRtt
Data Type: REG_DWORD
Valid Range: 0-65535 (decimal)
Default: 0xBB8 (3000 decimal)

The InitialRtt parameter controls the initial retransmission timeout used by TCP on each new connection. It applies to the connection request (SYN) and to the first data segment(s) sent on each connection. For example, the value data 5000 decimal sets the initial retransmit time to five seconds.

Value Name: TcpMaxDataRetransmissions
Data Type: REG_DWORD - Number
Valid Range: 0 - 0xFFFFFFFF
Default: 5

The TcpMaxDataRetransmissions parameter controls the number of times TCP retransmits an individual data segment (non connect segment) before aborting the connection. The retransmission timeout is doubled with each successive retransmission on a connection. It is reset when responses resume. The base timeout value is dynamically determined by the measured round-trip time on the connection.


The above text contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit and restore the registry, view the "Changing Keys and Values" and "Restoring the Registry" Help topics in Registry Editor (in Regedit.exe) or the "Add and Delete Information in the Registry", "Edit Registry Data", and "Restoring a Registry Key" Help topics (in Regedt32.exe).

Note that you should back up the registry before you edit it. If you are running MS Windows NT/2000, you should also update your Emergency Repair Disk (ERD).

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