Why is TCP socket communication not working in Windows 2008?

Question

Windows Server

There is a samopisny program the server and the client.
They communicate with each other over TCP sockets using WinAPI.

There are two VPS servers, new, rented from different providers.
With one server data exchange goes normally.
The client cannot connect to another server. (Connect failed error: (#10060) Connection timed out.)

In both cases, the IPs are public.
In the server firewall, the exchange port is open for incoming and outgoing connections.
Through netstat on the server writes that the port is open.
There are no antivirus firewalls or other blockers.

What could be? Why can't I connect to the server?

Answer 1

You can start by pinging the server, then test the connection via telnet:
telnet IP PORT
If you connect, the screen will be cleared and the connection may be immediately terminated (but not necessarily, depending on the server).
If telnet connects, then the problem is in the client software. If you do not connect, you need to check the entire chain from the server to the client, the blocking can be anywhere, incl. at the provider.