There are situations, which require the remote access to the
computer. For example, if the WWW server is a part o the
Control Web application, it is necessary to allow
users to access it from their computers. Another example is deploying
of distributed applications — one application is
divided into several parts, each running on the separate computer.
Individual applications need to share data, to notify about events
etc. It is necessary to configure the firewall to allow communication
over network.
Thorough description of firewall principles and configuration can
be found in the documentation published by Microsoft Corporation.
WWW server — the HTTPD virtual
instrument
The httpd virtual instrument, working as WWW server,
is a part of both Control Web 5
and Control Web 2000 distribution. If you
include this virtual instrument into your application and run the
application under Windows XP SP2, Windows Firewall blocks the
access to the web server from other computers. It also opens the
following warning dialog box:
If the user with administrative privileges is logged to the
system (either the Administrator or an user, who is a member of
Administrators group) he or she can directly unblock the
Control Web application. The Firewall adds the
Control Web to the list of applications with
allowed access to the network services. All other runs of the
application will perform without any problems with network access
granted.
If the currently logged user does not heave administrative
privileges, Windows Firewall displays notification message box.
Only administrators can allow applications to access network. It
is necessary to log on as Administrator to unblock Control Web.
To unblock an application manually, open Windows Firewall
applet from Control Panel (Control Panel can be opened from menu
Start -> Settings -> Control Panel).
Application allowed to access the network are listed in the
Exceptions tab. It is necessary to add Control Web to the list of unblocked applications.
Please note it is necessary to unblock both development and
runtime versions of Control Web separately. The
development version main executable (cw5.exe) and runtime version
main executable (cw5run.exe) are completely different applications
from the Firewall point of view.
Distributed applications
Configuration is more complex in the case of distributed
applications. Individual applications use the Control Web IPC
Service to establish the communication so it is necessary to
unblock it.
Control Web IPC Service
The Control Web IPC Service is a part of every
Control Web installation. It runs even before
any user logs into the system as an operating system service.
Control Web IPC is quite small program, but is used by both
development version and runtime version of Control Web to communicate with operating system, to
establish mutual network connections etc.
The Control Web IPC Service process is implemented in the
cwsvc.exe file. It is installed in the directory
\Program Files\Moravian Instruments\shared.
It is necessary to unblock this service (add it to the list
of applications allowed to access network) in the Windows
Firewall configuration. Steps necessary to unblock some
application are described in the previous chapter.
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