WebSocket Server

Context

You can connect PCo as a WebSocket server to Web applications. The following processes are supported:

Notification Process

The events provided by the source system can be displayed directly on modern user interfaces (for example, HTML5 interfaces) using the notification process. (See: Settings for the Notification Process with WebSocket.)

Example

You can use SAP MII's Self Service Composition Environment (SSCE) as a user interface. MII can send specific JSON messages to PCo to subscribe to tags. PCo then sends the changes to the user interface continuously.
Query Process

The connected client can send messages directly to the PCo WebSocket server. For example, you can query a specific tag in an OPC source system using a JSON retrieve message. PCo processes the query and returns a corresponding result.

Note

A WebSocket destination system is not needed in the query process.

Procedure

Select the WebSocket Server checkbox and make the following connection settings:

Field	Description
Allow Changes to Tag Values	Indicates that the tag values from the source system can be changed. If you select the checkbox, the tag values of the data source can be changed using store queries if the tag can be changed in the source system.
Unsecured Protocol	Select this connection setting if you want to use an unsecured protocol.
Secured Protocol (WSS)	Select this connection setting if you want the communication to run with a secured protocol. In this case, you need to assign a certificate in the Certificate field.
Port	Here you need to enter the PCo port through which the WebSocket connection is to be established and kept alive. Example SAP MII can be connected to PCo via a WebSocket. The MII system needs to be registered at the PCo port. To do this, in SAP MII, go to Data Service Data Server Connection and specify the PCo port in the WebSocket Port field.
Server Certificate	When using a secured protocol, you must assign a certificate here from the certificate store. You can use this certificate to identify PCo to the WebSocket-based client.
Request Client Certificate	Specifies that the client has to identify itself to PCo with a certificate. In the case of a WebSocket connection, the client is the Internet browser. If the indicator is set, the PCo server can ask that the client identifies itself with a certificate. This allows you to increase the security of the connection. However, for some browsers, it is not easily possible to request client certificates. In this case, deactivate the requesting of client certificates by deselecting the indicator. Note For a secure connection between the server (PCo) and a client, the server identifies itself with a certificate that you can assign here on the tab. The client can now check if the certificate is trustworthy. A certificate is trustworthy under the following circumstances: The certificate is in the certificate store of the PCo server Or the root certificate from which the server certificate has been issued is in the client's certificate store (in this case, this is the certificate store of the Internet browser)
Client Root Certificate	In this field, you can specify for the client the root certificate that is to be used to authenticate the client. The client certificate inherits the trustworthiness from the trusted root certificate. PCo only allows client certificates for the connection to the PCo WebSocket server that inherit from the specified root certificate. If you do not specify a root certificate, PCo allows all client certificates that inherit from a root certificate from Microsoft's trusted root certificate store (for example, Verisign) or from another trusted certification authority.
Message Format	Here you enter the data format for transferring the notification messages. The following data formats are available: JSON XML Note In the case of queries, PCo responds automatically in the format in which the query was made by the client.

To create a destination system for the WebSocket, choose the Create Destination System function key.

PCo creates the destination system automatically and displays the information Destination system used in configuration in the Status field. If no destination system exists, the information Destination system not created is displayed in the Status field.

Note

You can then select this destination system on the Destinations tab of the notification. The destination system is not displayed in the Destination Systems area, however.

The destination system enables PCo to send notifications later to all Web applications that have registered via the port you specified.
To delete the destination system, you can choose the Delete Destination System pushbutton. You can only delete the destination system if it is not being used in a notification.