Stun simple traversal of UDP over NATs

Stun( Simple Traversal of UDP over NATsNat UDP Simple Traversal) is a network protocol that allows clients located after Nat (or multiple Nat) to find their own public network addresses, find out which type of Nat You are located and the Internet port that Nat is bound to a local port. This information is used to establish UDP communication between two hosts after the NAT router at the same time. This Protocol is defined by RFC 3489.
Once the client learns the UDP port of the Internet, the communication can begin. If Nat is fully cone-shaped, either party can initiate communications. If Nat is a restricted cone or the port is restricted cone, both parties must start transmission together.
Note that you do not need to use the STUN Protocol to use the technology described in the stun RFC-you can also design another protocol and integrate the same functions into the server running the protocol.
Protocols such as sip use UDP to transmit audio and/or video data over the Internet. Unfortunately, because the two ends of the communication are usually after Nat, the traditional method cannot be used to establish a connection. This is where stun plays a role.
Stun is a client-server protocol. A VoIP Phone or software package may include a stun client. The client sends a request to the stun server. Then, the server reports to the stun client the public IP address of the NAT router and the port opened by Nat to allow incoming traffic to be sent back to the Intranet.
The above response also enables the stun client to determine the NAT type in use-because different NAT types process incoming UDP groups in different ways. Three of the four main types can be used: Fully cone-type Nat, restricted cone-type Nat, and port-restricted cone-type Nat. However, symmetric NAT (also known as bidirectional Nat) is often used in large companies) it cannot be used.