Connection establishment

Questions regarding the use of the UaExpert.

Moderator: uaexpert

Post Reply
datenRaten
Jr. Member
Jr. Member
Posts: 1
Joined: 16 Oct 2019, 09:55

Connection establishment

Post by datenRaten »

Hello,

I got a question regarding the connection establishment using UaExpert.
Tools used: UaExpert v1.5.1, OPC UA C++ Demo Server V1.7.0

When following the connection establishment process using wireshark, two phases can be observed.
First the sequence is: Hello -> Ack -> OpenSecureChannelRequest -> OpenSecureChannelResponse -> GetEndpointsRequest -> GetEndpointsResponse -> CloseSecureChannelRequest

Shortly after the "real" connection is established:
Hello -> Ack -> OpenSecureChannelRequest -> OpenSecureChannelResponse -> CreateSessionRequest -> CreateSessionResponse -> ActivateSessionRequest -> ActivateSessionResponse

Is this expected behaviour? The specification and other traces are telling me that the process can be done in a single step. Is there a special reason it is done this way by UaExpert?

background: The aim is to classify traffic (especially OPC UA) using a statistical approach. For that simulations of the connection establishment and data exchange are necessary and I'm not sure whether the case presented here should be considered.

User avatar
Support Team
Hero Member
Hero Member
Posts: 3064
Joined: 18 Mar 2011, 15:09

Re: Connection establishment

Post by Support Team »

Hello,

the "double" connection is the intended behaviour. A Client will typically discover the available endpoints in a first step and in a second step connect for the "real". A good client will even check if for both connection approach the server returned the same security relevant data.
Best regards
Unified Automation Support Team

Post Reply