This error indicates that a client certificate is required in this handshake.

I suggest to capture a wireshark log for your network connection (without vugen recording) and check if a certificate is required or not (sslkey may be required to deprecate the data); you can also capture the network data for vugen recording and do a comparison to see what is missed in your script.

Thank you for the reply, unfortunately we do not have access the the application that interfaces over TCP with our System Under Test so we cannot record the traffic from the application over wireshark or via vugen. 

We have had to manually put the request together and ensure the TCP connection is correct via working with the System Under Test Engineers - we know a client certificate is required from discussing with those engineers we just don't know how to make vugen present a certificate as it is currently not sending anything, is there a way to add a certificate to a handcrafted socket / request?

Cameron Jones ,

You might explore the function web_set_certificate_ex() and SSL Utility.

Cameron Jones ,

You might explore the function web_set_certificate_ex() and SSL Utility.

Does the  web_set_certificate_ex() function work on a Windows Sockets protocol script?