Is it possible to send files between computers without using a server?

Question

Computer networks

I have a question. Is it possible to send a file between computers without using a server? If these two computers do not have a white ip and are in different cities. For example, how does the connection work with Hamachi? Maybe a stupid question, but please answer. Thanks in advance.

Answer 1

To transfer without using an intermediate server, you need a real address for at least one computer and some software - an FTP server, for example. If both computers have a gray address, then it all depends on the provider. It happens that the address is gray in the sense that it changes, but if you know it, you can connect directly. This is the basis for the operation of services such as DDNS - the address changes, but the name is bound each time to a new address and you can work by connecting by name. It worked with wired providers, and it probably still works. With cellular operators - no, there it is an additional service.

Answer 2

Programs like Hamachi use various methods to establish a direct connection between two points behind NAT. See STUN/TURN, ICE. You will need some kind of server to negotiate the connection, but you can transfer data directly.
https://en.wikipedia.org/wiki/Interactive_Connecti...
There are ways to establish a direct connection without a server at all: starting from the banal sending of a UDP packet from each side to the other side, with fixed source and destination ports, ending with pwnat .