Port Quest: Communication Portals in the Digital World

Ports are not only key nodes for information transmission, but also links for system function control. Similar to the closed loop of a system program, it needs to receive instructions and adjust its functions accordingly to serve user needs. This closed loop is cut into many segments, and these interfaces are what we often call ports. The opening and closing status of the port determines the system's response to external instructions and data input.

TCP and UDP are two important protocols in network communication. As a reliable, connection-oriented transport layer protocol, TCP has a clear port range; while UDP provides simple, connectionless information transmission services. Both have independent port numbers, but there are differences between common ports and dynamic ports.

Common ports usually range from 0 to 1023, such as port 80 for WWW service, port 21 for FTP service, etc. In addition to the default port, users can also use other port numbers, but the port numbers of some system protocols are fixed. For example, port 139 is specifically used for NetBIOS and TCP/IP communication and cannot be changed manually.

Dynamic ports usually range from 49152 to 65535. The reason why it is called a dynamic port is that it generally does not allocate a certain service fixedly, but dynamically allocates it as needed.

In addition, the port number range commonly used by user processes or applications is from 1024 to 49151. These ports are free for users to use when not occupied by server resources.

For novices, port protection is particularly important. They are often highly vigilant about their own ports and are worried about opening too many ports, especially the presence of backdoor programs. However, protecting your own ports is not a complicated matter. We only need to ensure the security of the port through simple steps such as viewing, judging and closing. When making judgments, we need to be cautious to avoid misjudgments due to dynamically allocated ports or some common ports. In addition, we also need to always be wary of some cunning backdoor software, which may use some common ports to communicate, thereby bypassing our firewall and bringing security risks to our systems. Therefore, we need to be more cautious when running some unknown programs.