Method for Controlling the Direct Penetrate Communication Two Parts of Which Are Under the Different Nats and the Device Thereof

A method for checking, in a user device under a NAT, whether a selected local source port is a penetrated port or not, comprising the steps of:

• selecting a local source port;
• sending times of detection messages through said source port and via said NAT to a plurality of destination ports on an auxiliary detecting device in an external network or to a plurality of auxiliary detecting devices in an external network;
• receiving a detection reply message from said auxiliary detecting device(s) in the external network, wherein the content of said detection reply message comprises NAT source address and NAT port which correspond to said detection message on said NAT;
• obtaining NAT-translated NAT source address and NAT source port of said detection message;
• judging that said local port is a local penetrated port which does not conflict with the port of other device, if NAT source ports of the times of detection messages are the same as one another;
• otherwise, re-selecting a different local source port, and repeating the aforesaid steps until a proper port is found.

A use device under a NAT, which is for implementing direct penetrating communication with a user device under a different NAT through a specific local port, the user device having a plurality of network ports, further comprising:

• a selecting means for selecting a local source port for sending and receiving messages;
• a detecting means for obtaining NAT source address and NAT port, which correspond to said local source port on a NAT;
• a port information exchanging means for notifying another user device under other NAT of said NAT source address and NAT port via a notifying device in an external network, and learning NAT external-network address and NAT port of the user device under said another NAT via the notifying device in the external network,
• wherein said user device and the opposite-end user device directly communicate with each other through said local source port with the received NAT external-network address and NAT port of the other party as a destination address.

A method for helping, in an auxiliary detecting device in an external network, a user device under a NAT to obtain a NAT port corresponding to its local source port, comprising the step of:

• receiving a detection message from said user device;
• parsing the received detection message to obtain source address and source port information of the message;
• and
• sending the source address and source port information of the parsed message to said user device via a reply message.