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  • Writer's pictureDestek Ekibi

Properties of the Web server

Benefits of the web server

The web server enables monitoring and administering of the CPU by authorized users over a network. Evaluations, diagnostics, and modifications are thus possible over long distances. Monitoring and evaluation is possible without STEP 7, only a web browser is required. Note that you must take appropriate measures to protect the CPU from compromise (such as restricting network access, using firewalls).

Activating the web server

​The web server is deactivated in the delivery state of the CPU. This means that you must load a project in which the web server is activated to enable access using the web browser.

Security functions

​The web server provides the following safety functions:

·​Access via the secure transmission protocol "HTTPS" using the CA-signed web server certificate

·​User authorizations you can configure by means of user list

·​Activation for specific interfaces

Web browser

​You need a web browser to access the HTML pages of the CPU.

​The web browsers listed below have been tested for communication with the CPU. Other web browsers may also work, especially newer versions. However, if problems occur with web browsers not mentioned here that cannot be rectified, use one of the following tested web browsers:

·​Microsoft Internet Explorer (Version 11.0)

·​Microsoft Edge (Version 100.0)

·​Google Chrome (Version 100.0)

·​Mozilla Firefox (Version 90.0)

·​Opera (Version 85.0)

·​Mobile Safari and Chrome for iOS (iOS 12.5.1)

·​Android browser (7.x, 8.x and 10.x)

·​Chrome for Android (7.x, 8.x and 10.x)

·​HMI Panels:

· ​Basic Panel

· ​Comfort Panel


​If you are using Internet Explorer, deactivate "Compatibility view" in the settings ("Options" menu).


​For access to display devices with low screen resolution, we recommend the use of basic web pages, see section ​Basic websites​.


​Older versions of the web browsers named above, which previously supported access to the HTML pages of the CPU, continue to allow this. However, these older versions do not support the new functions and HTML pages described in this edition.


​Two reserved communication connections are available to the web server for communication with the CPU.

​Depending on the web browser used, different numbers of connections to the CPU are established. If more connections are available, more communication connections will be established.

​If no more connections are available, display or functional problems may occur. This is because the web server will reject all other communication connections apart from the two that are reserved. ​For this reason, the web pages may not load fully.


​If you access the web server of the CPU using a communications processor (CP), ensure that the cache (temporary Internet files) is activated in your web browser. Choose the "Automatically" option in the cache settings of your web browser.

​If the cache is deactivated or if a setting other than "Automatically" is made in the cache settings of your web browser, this may result in slow access times and incomplete display.


​After a firmware update of the CPU, incorrect display of web pages can occur in various web browsers. This is caused by problems of the new CPU firmware with the cache of the web browser.

Solution:​ Press F5 or clear the web browser cache.


​Web browser behavior can be different if a certificate is not valid yet or is no longer valid. Siemens has no influence on this behavior. This means we cannot guarantee the reliable functionality of the web server with invalid certificates.

Reading out data

​With the web server, you can read out the following data from the CPU and, in some cases, modify and write back the data to the CPU.

·​Information on ​Diagnostics

· ​Identification

· ​Program protection

· ​Memory

· ​Runtime information

· ​Fail-safe (with an F CPU)

·​Contents of the ​diagnostics buffer

·​Information on ​Communication

· ​Important interface parameters

· ​Port statistics

· ​Display of the communication resources

· ​Display of the communication connections


· ​Graphical view (set and actual topology)

· ​Table view (actual topology)

· ​Status overview

·​Reading out ​service data

​The HTML pages are described in more detail on the following pages.


Max. characters at data type WSTRING

​Note that the data type WSTRING is limited to 254 characters for the display in the web server. If the 254 characters are exceeded, the web server does not display the superfluous characters.

Web access to the CPU via PG/PC, HMI devices and mobile end devices

​Proceed as follows to access the web server:

1. ​Use STEP 7 to download a project in which the web server is activated to the CPU.

2. ​Connect the display device (PG/PC, HMI, mobile terminal device) with the CPU or a communication module using a PROFINET interface. ​If you are working with WLAN, activate the WLAN on the display device and establish a connection to the access point (e.g. SCALANCE W788-1RR or SCALANCE W784-1), which is in turn connected to the CPU.

3. ​Open the web browser on the display device.

4. ​Enter the IP address of the interface of the CPU which is connected to the client in the "​Address​" field of the web browser in the following format: https://a.b.c.d (entry example: ​The introduction page of the CPU opens. From the intro page you can navigate to more information.

​More information on access using the secure transmission protocol "HTTPS" is available in the section ​Configuring the Web server​.

More information

​Using a smartphone, you can access the web server of the CPU either via WLAN or access to the CPU via the SIMATIC S7 app (using web server functionality). You can find additional information in the FAQ entry ID 103473392 on the ​Service&Support​ Internet page.

​Note: The web server must also be activated for access to the CPU via the SIMATIC S7 app.

​The SIMATIC S7 app offers you additional functions. You can find a detailed application example with further documentation and example projects on the ​Service&Support​ Internet page.

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