When following the Http/1.1 protocol, RFC 2616 section 8.1.4, it reads:
‘A single-user client SHOULD NOT maintain more than 2 connections with any server or proxy. A proxy SHOULD use up to 2*N connections to another server or proxy, where N is the number of simultaneously active users. These guidelines are intended to improve HTTP response times and avoid congestion.’
So in conclusion the problem was not with a server restriction but with a client restriction.
The solution is to change the connection limit in your client program. You can do this programmatically.
For .NET c# the following can be used: ServicePointManager.DefaultConnectionLimit = 10;