Can p2p networks work if all users have gray IPs?

Question

Computer networks

Do I understand correctly that a distributed network on any protocol that works only via the Internet (without servers) cannot function if all participants in this network have gray (not visible from the external Internet, located behind the provider's router) ip addresses?

Interested in the option only without servers. Incl. without signaling servers and other "pillars", without port forwarding and any other transformations in the way participants connect to the Internet.

Answer 1

Another builder of an independent protest messenger? :D
No, they can't.
Kazakh practice has shown that the only "messenger" that is difficult to control are portable radios :)

Answer 2

In general, without any supports with white ip.

then they won’t be able to
tcpip requires someone to connect to someone by ip address,
but a situation is possible when a client connects to another client using white ip once, which opens ports on the router using upnp, remembers all such clients and transfers their entire list ( id_client:ip:port) to all clients.
If you promptly transfer information about changes in client ip addresses (such clients still remember the addresses of others and immediately inform others about it when they change their address), then this cloud of clients can exist in principle without a signal server (more precisely, other clients can be signal servers)
If the client disconnects from this network for a long time, it may turn out that all other clients will change their ip address and he will have nowhere to connect, but the more clients on the network, the more likely it is that a client with a permanent ip address will appear.
ps udp connection allows you to connect to someone else's connection without upnp support on the router

Answer 3

A direct connection of two clients behind NATs, if at least one of them is not symmetric (symmetric nat), is possible using UDP and TCP hole punching, but for this you need to know the IP addresses and ports of both sides.
There is also a way to determine the IP address of the client by the server - ICMP Hole Punching , implemented in the pwnat program , but sending a packet by the client requires administrator rights on the device, and the packet may also be dropped by some firewalls.
Can p2p networks work if all users have gray IPs? Yes, they can, but not always and not as stable as with a full direct connection.

Answer 4

the "signaling" server is primarily used to connect clients. then clients communicate directly

Answer 5

Can you send a letter to a friend without knowing his address, full name, but only knowing that he is somewhere in the world?

Answer 6

Since there is no "not in the same local network" in your restrictions, they can. "No port forwarding" - but some are "forwarded" by default. Without 80 the web will not work, for example. That is, if someone from the local party manually connects to another local network through the default port, he will be able to transfer connection data to the others. You can save this data and try to use it in other cases. Lists of nodes can be transferred to other networks, supplemented and received back.

Answer 7

They can if there are virtual ip addresses like vpn