It can be said that a port is a way for a computer to communicate with the outside world. Without it, the computer would be deaf and dumb.
In network technology, ports have several meanings. The ports of hubs, switches and routers refer to the interfaces connecting other network devices, such as RJ-45 port and serial port. The port we are talking about here is not a physical port, but a port in TCP/IP protocol, which is a logical port.
So what does the port in TCP/IP protocol mean? If the IP address is compared to a house, the port is the door of the house. A real house has only a few doors, but an IP address can have 65536 ports! Ports are marked by port numbers, which are only integers from 0 to 65535.
What's the use of ports? As we know, a host with an IP address can provide many services, such as Web services, FTP services, SMTP services and so on. These services can be completely realized through 1 IP address. So, how does the host distinguish different network services? Obviously, you can't just rely on ip addresses, because IP addresses and network services have a one-to-many relationship. In fact, different services are distinguished by "IP address+port number".
It should be noted that the ports are not in one-to-one correspondence. For example, when your computer accesses a WWW server as a client, the WWW server uses "80" port to communicate with your computer, but your computer may use "3457" port, as shown in figure 1.
Figure 1
According to the corresponding protocol type, there are two kinds of ports: TCP port and UDP port. Because TCP and UDP are independent, their respective port numbers are also independent of each other. For example, TCP has 235 ports, and UDP can also have 235 ports. There is no conflict between them.
How are the ports allocated?
Port numbers, like IP addresses, are not used at will, but are assigned according to certain regulations. There are several classification standards for ports. I won't explain it in detail here, but only introduce the well-known ports and dynamic ports.
1. well-known port
Well-known ports are well-known port numbers ranging from 0 to 1023, of which 80 ports are allocated to W WW service and 2 1 ports are allocated to FTP service. We don't need to specify a port number when entering a URL (such as cce) in the address bar of IE, because the port number of WWW service is "80" by default.
Network services can use other port numbers. If it is not the default port number, you should specify the port number in the address bar by adding a colon ":"(half angle) after the address and then adding the port number. For example, if you use "8080" as the port of WWW service, you need to enter "gonet8 gonet8:8080" in the address bar.
However, some system protocols use fixed port numbers and cannot be changed. For example, port 139 is specially used for communication between NetBIOS and TCP/IP and cannot be changed manually.
2. Dynamic port
Dynamic ports range from 1024 to 65535. It is called a dynamic port because it generally does not allocate a service fixedly, but dynamically. Dynamic allocation means that when a system process or an application process needs network communication, it applies for a port from the host, and the host allocates an available port number for it to use. When this process is shut down, it also releases the occupied port number. ...& gt& gt
What is a broadband port?
Computer "port" is the literal translation of English port, which can be regarded as the exit of computer communication with the outside world. Among them, the ports in the hardware field are also called interfaces, such as USB ports and serial ports. Ports in the software field generally refer to communication protocol ports in the network for connected services and connectionless services. They are abstract software structures, including some data structures and I/O buffers. According to the port number, it can be divided into three categories: (1) well-known ports: from 0 to 1023, which are closely bound to some services. Usually, the communication of these ports clearly indicates the protocol of a certain service. For example, port 80 has always been HTTP communication. (2) Registration port: from 1024 to 49 15 1. They are loosely bound to some services. In other words, many services are bound to these ports, and these ports are also used for many other purposes. For example, many systems handle a dynamic port of about 1024. (3) Dynamic and/or dedicated ports: from 49 152 to 65535. Theoretically, these ports should not be assigned to services. In fact, machines usually allocate dynamic ports from 1024. But there are exceptions: SUN's RPC port starts at 32768. Some ports are often used by hackers and Trojan viruses to attack computer systems. The following is the introduction of computer ports and the brief methods to prevent being attacked by hackers. 8080 port description: 8080 port, like 80 port, is used for WWW proxy service and can realize web browsing. When visiting a website or using a proxy server, the port number ":8080" is often added, such as cce:8080. Port vulnerability: Port 8080 can be used by various virus programs. For example, the BrOwn Hole (Bro) Trojan virus can completely remotely control an infected computer using port 8080. In addition, RemoConChubo and RingZero trojans can also use this port to attack. Operation suggestion: Generally, we use port 80 for web browsing. In order to avoid virus attacks, we can close this port. What the landlord said about port radiation should be port surveying and mapping. If you are a broadband access user such as ADSL, CABLE MODEM and optical fiber, and want to build a game server or WEB server in an Internet cafe or company, so that users on the Internet can access your server, then you will encounter the problem of port mapping. Usually, routers have firewall function. Internet users can only access the WAN port of your router (connected with ADSL line port) and cannot access the internal server. If you want external users to access the server, then you have to make a forwarding setting on the router, that is, port mapping setting, so that the user's request can reach the game server or WEB server after reaching the router. This is the port mapping. At present, all broadband routers have port mapping function, but each router manufacturer takes different function names, some are called virtual servers, and some are called NAT settings. . . Port mapping settings are very simple. For example, to map a WEB server with an IP address of192.168.1.254, just fill in the server's IP address192.1.
What does the port mean?
Ports are divided into three categories.
1) well-known ports: from 0 to 1023, which are closely bound with some services. Usually, the communication between these ports clearly indicates some service protocol. For example, 80 ports have always been h++p communication.
2) Registration port: from 1024 to 49 15 1. They are loosely bound to some services. In other words, many services are bound to these ports, and these ports are also used for many other purposes. For example, many systems handle a dynamic port of about 1024.
3) Dynamic and/or dedicated ports: from 49 152 to 65535. Theoretically, these ports should not be assigned to services. In fact, machines usually allocate dynamic ports from 1024. But there are exceptions: SUN's RPC port starts at 32768.
This section describes the information of TCP/UDP port scanning in firewall records.
Remember: there is no such thing as an ICMP port. If you are interested in interpreting ICMP data, please refer to other parts of this article.
0 is commonly used in analytical systems. This method works because "0" is an invalid port in some systems. When you try to connect it with an ordinary closed port, it will produce different results. Typical scanning: use the IP address 0.0.0.0, set the ACK bit and broadcast it in the Ethernet layer.
1 tcpmux this means that someone is looking for the SGIIrix machine. Irix is the main provider of tcpmux, which is turned on by default in this system. Iris machine contains several default password-free accounts when it is released, such as LP, Guest, UUCP, NuUCP, Demos, Tutor, Diag, EzSetup, OutofBox,
And 4d gifts. Many administrators forget to delete these accounts after installation. So hackers searched for tcpmux online and used these accounts.
7Echo You can see the messages sent by many people to x.x.x.0 and x.x.x.255 when searching for the Fraggle amplifier. A common DoS attack is echo-loop. The attacker forges UDP packets sent from one machine to another, and the two machines respond to these packets in the fastest way. (See Chargen) Another thing is to double-click the TCP connection established at the word port. There is a product called Resonance Global Scheduling, which connects with this port of DNS to determine the nearest route. Harvest/squid cache will send UDPecho from port 3 130: "If the source_ping on option of the cache is turned on, it will send a hit reply to the UDP echo port of the original host." This will generate many such packets.
1 1 sysstat This is a UNIX service that lists all running processes on the machine and the reasons for starting them. This provides a lot of information for intruders, threatening the security of the machine, such as exposing some known weaknesses or accounts. This is similar to the result of "ps" command in UNIX system. Say it again: ICMP has no port, and ICMP port 1 1 is usually ICMP type =119. This is a service that only sends characters. The UDP version will respond to packets containing junk characters after receiving UDP packets. TCP company
After the connection, the data stream containing junk characters will be sent until the connection is closed. Hackers can use IP spoofing to launch DoS attacks and forge UDP between two chargen servers. Because the server tries to respond to the infinite round-trip data communication between two servers, a chargen and an echo will overload the server. Similarly, the fraggle DoS attack will broadcast a packet with a forged victim IP to this port of the target address, and the victim will overload it in response to the data.
2 1 ftp The most common attacker uses ... >>
What does broadband port binding mean?
Port binding means that your broadband account is bound to your network card address. Changing the network card or router causes the port to be bound with different network card addresses, and the network cannot be accessed. Clear binding can get on the internet.
In this case, don't call 10000 to report the fault, but complain, and don't say that you used the router. Basically, people who bind ports are not allowed to use routers. Suppose you have two computers, a desktop and a laptop. This can't be used by another computer after surfing the internet. Please cable it for you. General Telecom will unbind your port.
What is an Ethernet port?
It is to insert network equipment such as I router and switch into the network cable port.
What is a single-port network?
In network technology, ports have two meanings: one is physical ports, such as interfaces used by ADSL modems, hubs, switches and routers to connect other network devices, such as RJ-45 ports and SC ports; The second is logical port, which generally refers to the port in TCP/IP protocol. Port numbers range from 0 to 65535, such as port 80 for browsing web services, port 2 1 for FTP services and so on.
Question: What do the service port and monitoring port in the network port mean respectively? thank you
The server refers to the client computer and the monitoring end is the server control center.
What does monitoring mean in network port management? Still in touch?
Port monitor means that after receiving an IP packet, the host network process checks whether its target port is its own port number, and if so, it accepts the packet for processing. The main difference between links and links is that links establish a data transmission mechanism, while listeners do not.
What does the green light and yellow light of the network cable port mean?
Network devices such as network cards and switches are different. Generally speaking, the green light is on or off (representing the network speed), and the yellow light is on or off (representing whether to send or receive data).
Green light: long light represents100m; No light means 10M.
Yellow light: Long light indicates that no data is sent or received; Blinking indicates that data is being sent and received.
There are also some gigabit network cards with lights divided into * * *. If they don't light up, it means 100M/ green means 1000M/ yellow means 1000m, and now the network of 100m is basically invisible. If one light is on all the time, the basic explanation is that the network of 100 m is higher, while the other is.
What does broadband installation port mean?
That is, the operator pulls in the broadband port of your community. If there is no logging operator in your community, it is impossible to install broadband. It is equivalent to the fact that there is no cell phone signal transmission in your community, so you can't make a phone call.