simple question about function call syntax

[Nikolay via Digitalmars-d-learn]

I found this code sample in vibe:

void connect(NetworkAddress addr)
        {
		enforce(.connect(m_ctx.socketfd, addr.sockAddr, 
addr.sockAddrLen) == 0, "Failed to connect UDP 
socket."~to!string(getLastSocketError()));
        }
What does mean ".connect"? Where I can find description of this 
syntax (dot + function name)?