This is the NAT test for me (Windows 10):
Spoiler
Using server nntest.cnc-online.net:30000
Bound to local port 57616
Bound to local alternate port 57617
Resolving hostname 'nntest.cnc-online.net'...
Resolved server host to be '37.247.49.213'
Sending client INIT from port 57616 to nntest.cnc-online.net:30000
Received server INIT [471011]
Our public address is 217.237.42.133:57616
Sending client INIT2 [471011] from port 57617 to nntest.cnc-online.net:30000
Received server INIT2 [471011]
Our alternate public address is 217.237.42.133:57617
Sending cient START [471011] from port 57617 to nntest.cnc-online.net:30000
Received server START [471011]
Server extra port is 40000
Sending client PING [471011] from port 57616 to nntest.cnc-online.net:40000
Received server PING(1) [471011]
Received server PING(2) [471011]
Received server PING(3) [471011]
===========
SUCCESS
===========
Received 3 pings from nntest.cnc-online.net:40000.
NAT negotiation works with your router and connection.
==> You do not have to use port forwarding.
Drücken Sie eine beliebige Taste . . .
This one is the test for Friend A (Windows 10)
Spoiler
Using server nntest.cnc-online.net:30000
Bound to local port 55134
Bound to local alternate port 55135
Resolving hostname 'nntest.cnc-online.net'...
Resolved server host to be '37.247.49.213'
Sending client INIT from port 55134 to nntest.cnc-online.net:30000
Received server INIT [525700]
Our public address is 87.158.88.25:55134
Sending client INIT2 [525700] from port 55135 to nntest.cnc-online.net:30000
Received server INIT2 [525700]
Our alternate public address is 87.158.88.25:55135
Sending cient START [525700] from port 55135 to nntest.cnc-online.net:30000
Received server START [525700]
Server extra port is 40000
Sending client PING [525700] from port 55134 to nntest.cnc-online.net:40000
Received server PING(2) [525700]
Received server PING(3) [525700]
Received server PING(4) [525700]
===========
SUCCESS
===========
Received 3 pings from nntest.cnc-online.net:40000.
NAT negotiation works with your router and connection.
==> You do not have to use port forwarding.
And this one is the test for Friend B (Windows 7)
Spoiler
Using server nntest.cnc-online.net:30000
Bound to local port 62426
Bound to local alternate port 62427
Resolving hostname 'nntest.cnc-online.net'...
Resolved server host to be '37.247.49.213'
Sending client INIT from port 62426 to nntest.cnc-online.net:30000
Received server INIT [113650]
Our public address is 95.90.206.128:4276
Sending client INIT2 [113650] from port 62427 to nntest.cnc-online.net:30000
Received server INIT2 [113650]
Our alternate public address is 95.90.206.128:4225
Sending cient START [113650] from port 62427 to nntest.cnc-online.net:30000
Received server START [113650]
Server extra port is 40000
Sending client PING [113650] from port 62426 to nntest.cnc-online.net:40000
Received server PING(1) [113650]
Received server PING(2) [113650]
Received server PING(3) [113650]
===========
SUCCESS
===========
Received 3 pings from nntest.cnc-online.net:40000.
NAT negotiation works with your router and connection.
==> You do not have to use port forwarding.
My bad, I forgot to post these when I started the topic