Port mapping does not ask for people

Now most home and office LANs share the Internet through NAT. Because NAT works to hide the internal IP address from the outside world, it constitutes a natural firewall. For this reason, the external services on some hosts cannot be directly accessed by the external network users. The external service port of the internal network host must be mapped to the relevant port of the external IP address of the gateway through the port mapping method on the gateway. Can be accessed by the Internet.

Home and small office LAN sharing Internet is mainly divided into soft (proxy server) and hard (modem and broadband router with routing function). This article will explain the setting methods and steps of the two proxy methods in more detail with four practical cases.

The gateway address of the LAN is assumed to be 192.168.1.1, and the host address of the intranet server to be mapped is 192.168.1.3.

Example 1: FTP server. For example, in this paper, the mapping FTP server (TCP port 21) service is taken as an example. The mapping method of the WEB server is exactly the same as FTP, except that the port number is 80.

Example 2: CS server. The service port scanned by the CS client by default is TCP 27015~27017, so we take the mapping of port 21015 as an example. In fact, the mapping method with the FTP and WEB service ports is exactly the same.

Example 3: BT download. Since the principle of BT download is to upload at the same time of downloading, only uploading smooth can reach the high speed of downloading, so we need to map its upload port. Depending on the BT software used, for example, the Bit Wizard defaults to 16881 for all tasks. Other common BT download softwares use one upload port for each task. The starting port is TCP 6881, which generally allows 10 tasks. Therefore, the mapping of ports 6881 to 6890 is taken as an example.

Example 4: QQ voice chat. QQ language chat is generally through the server transfer to establish a connection, so NAT has no effect on it. However, Tencent has restricted the non-members. The non-members who are in the chat are both behind the agent and cannot connect successfully. However, as long as one party belongs to the public network user, the connection is successful, and the member is not subject to this restriction. Therefore, in general, there is no need to map ports.

And when we encounter unsuccessful chats, most of them only open HTTP proxy on the gateway. Although QQ now supports HTTP proxy, QQ can only chat with HTTP proxy. When people chat outside, they always fail to connect. This situation can be solved by means of a secondary agent, and the setting method will be introduced in CCPRoxy.