Hi rvkvino,

Indeed a VPN should be transparent from the client's point of view, and therefore no special configurations in Lightstreamer are needed.

But, what can be the cause of the issue are restrictions imposed by the network environment outgoing the VPN of the customer involved. For example, there may be restrictions in the range of TCP ports enabled and maybe the 8080 port you use is not allowed.
Could you verify if these restrictions actually exist?

Regards,
Giuseppe