Port number-the identification number of the application software with network function. Note that the port number is not fixed, that is, it can be assigned manually by the user (of course, it is usually defined when writing software). Of course, many applications recognize the default ports, such as FTP: 20 and 2 1, http: 80, telnet: 23 and so on. I won't list them here. A software can have multiple port numbers, which proves that the software has more than one network function.
0- 1023 is a recognized port number, that is, it has been recognized or reserved for the software to be recognized, while 1024-65535 is a port number that has not been defined by public * * *, and users can define the functions of these ports themselves.
So what does the port number do? Please continue reading.
When a computer starts a program that can be accessed remotely by other computers, it must open at least one port number for external access. We can regard a computer without a port number as a sealed room. Of course, a sealed room cannot be accessed by the outside world, so when the system opens a program that can be accessed by the outside world, it is natural to open a window in the room to receive external access. This window is the harbor.
So why do you want to distinguish the ports by numbering them? Since a program has opened a port, can't all external information access Sichuan through this open port? The answer is no, why? Because data uses port numbers to inform which software the transport layer protocol is sent to for processing, data is unwise. If many programs * * * use one port to receive data, then when a packet is sent from the outside, the transport layer doesn't know which software to send for processing, which will inevitably cause confusion.
The Layer 4 header of a data segment encapsulated by the OSI Layer 4 transport layer mentioned last time contains two port numbers, namely the source port number and the destination port number. The function of the destination port number has been introduced above. Let us know the original port number.
The source port number is generally a number between 1024-65535 dynamically generated by the system itself. When computer A accesses computer B through the network, if the other party needs to return data, it will also randomly create a port larger than 1023, telling B which port to send data to when returning data, and then the software will start listening to this port and wait for the data to return. B After receiving the data, it will read the source port number and destination port number of the packet, and then record it. When the software creates the data to be returned, it will take the original port number in the original data packet as the destination port number and its own port number as the original port number, that is, it will reverse the original and destination in the received data packet and send it back to A. A will repeat this process until the data transmission is completed. When all data is transmitted, the source port is released, so the same software does not necessarily have the same source port number every time it transmits data.
What is the port number of 10658338?
Mobile Group electronic certificate Platform Port (Free)
What does the port mean?
Computer "port" is the 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.
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. There are only a few doors in a real house, but an IP address can have as many as 65536 ports (that is, 256×256)! Ports are marked by port numbers, which are only integers between 0 and 65535(256×256).
On the Internet, each host sends and receives datagrams through TCP/TP protocol, and each datagram is routed according to the ip address of its destination host. It can be seen that there is no problem in successfully sending datagrams to the destination host. What's the problem? We know that most operating systems support multiple programs (processes) running at the same time, so which process should the destination host send the received datagram to? Obviously, this problem needs to be solved, so the port mechanism is introduced.
The local operating system will assign protocol ports to those processes that need them, and each protocol port is identified by a positive integer, such as 80,139,445, and so on. After receiving the datagram, the destination host will send the data to the corresponding port according to the port number of the message header, and the process corresponding to this port will receive the data and wait for the arrival of the next group of data. Speaking of which, the concept of port still seems abstract. Keep following me and don't go away.
A port is actually a queue. The operating system allocates a different queue for each process. Datagrams are pushed into the corresponding queue according to the destination port, waiting to be accessed by the process. In extremely special cases, this queue may overflow, but the operating system allows each process to specify and adjust its own queue size.
Not only does the process of receiving datagram need to open its own port, but also the process of sending datagram needs to open the port, so that the active port will be identified in the datagram, so that the receiver can successfully return the datagram to this port.
What is the network port number?
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. ...
What do IP addresses and ports mean?
Computers on the network (whether local area network or Internet) are identified by IP addresses. Computers or applications installed on computers communicate with each other through communication ports.
There are two types of ports: TCP and UDP. In order to make some applications run normally, it is sometimes necessary to open the ports used by these applications in the firewall. Usually, the documents that come with these applications describe the ports they use and the ports that should be opened in the firewall. You can open specific ports in the firewall by creating custom connection permissions for the selected installed programs.
What is the server port number?
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. What I want to introduce here is the 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. The port number is the key to open the gate. 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".
Servers are usually identified by well-known port numbers. For example, for each TCP/IP implementation, the TCP port number of FTP server is 2 1, the TCP port number of Telnet server is 23, and the UDP port number of TFTP (Simple File Transfer Protocol) server is 69. Services provided by any TCP/IP implementation use well-known port numbers between 1 and 1023. These well-known port numbers are managed by the Internet Assigned Numbers Authority (IANA).
To 1992, the well-known port number is between 1 ~ 255. Port numbers between 256 and 1023 are usually occupied by Unix systems to provide some specific Unix services-that is, to provide some services that only Unix systems can provide, while other operating systems may not. IANA manages all port numbers between 1 and 1023.
One difference between Internet extension services and Unix-specific services is Telnet and Rlogin. They all allow you to log on to other hosts through the computer network. Telnet is a TCP/IP standard with port number 23, which can be implemented on almost all operating systems. Rlogin is only designed for Unix systems (although many non-Unix systems also provide this service), and its famous port number is 5 13.
The client usually doesn't care about the port number it uses, just make sure that the port number is unique on the machine. Customer port number is also called temporary port number (that is, short-lived). This is because it usually exists only when the user runs the client program, while the server runs its service as long as the host is turned on.
Most TCP/IP implementations assign port numbers between 1024 and 5000 to temporary ports. Port numbers greater than 5000 are reserved for other servers (services that are not commonly used on the Internet). We can see many examples of assigning port numbers to temporary ports later.
Solaris2.2 is a famous exception. Generally, the default temporary port number of TCP and UDP starts from 32768.
The above is taken from Baidu Encyclopedia. baike.baidu/...iVNkAI ...
What is the port number of 1062 1940?
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 China network technology, ports have several meanings. The ports of hubs, switches and routers refer to the interfaces connecting other China network devices, such as RJ- 4 5 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. There are only a few doors in a real house, but an IP address can have as many as 55 or 3 ports! Ports are marked with port numbers, which are only integers ranging from 0 to 55.35. 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 an IP address. So, how do hosts distinguish different China network services? Obviously, we can't just rely on ip address, because IP address and China network service 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 is used as a client to access the WWW server, the WWW server uses the "BA0" port to communicate with your computer, but your computer may use the "345 paint" 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, and the two do not conflict. 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 ports are well-known port numbers, ranging from 0 to 1023, where 0 port is assigned to W WW service and 2 1 port is assigned to FTP service. When we enter a China address in the address bar of IE (for example, to the United States, cce, China and China), we don't need to specify the port number, because by default, the port number of WWW service is "Bar 0". China network service 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 "Ba 0 Ba 0" as the port of WWW service, you need to enter "Zhimei". Gonet, China gonet, China: Ba 0 Ba 0 "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 Ports Dynamic ports range from 1024 to 5535. 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 China network communication, it applies for a port to 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.
What is the port number of China Mobile SMS?
China mobile short message center service number coding rules are:
1, +86 1380+ the four-digit long-distance area code of the account opening branch +500, and if the long-distance area code is less than four digits, add "0" to complete it (for example, Beijing +86 13800 100500).
2. You can also call the local mobile service center at 10086.
What is the host name and port number?
The name of the computer is the host name!
Port number: In network technology, ports include logical ports and physical ports. Physical ports refer to physically existing ports, such as interfaces on ADSL modems, hubs, switches and routers for connecting other network devices, such as RJ-45 ports and SC ports. Logical port refers to the port used to distinguish services in a logical sense, such as the service port in TCP/IP protocol. Port numbers range from 0 to 65535, such as port 80 for browsing web services and port 2 1 for FTP services. Due to the large number of physical ports and logical ports, in order to distinguish the ports, each port is numbered, which is the port number.
What is the 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 can be divided into three categories:
(1) Well-known ports: from 0 to 1023, which are closely bound with 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.
World Wide Web publishing service
Port description: Port 8080, like port 80, is used for WWW proxy service, which 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.
Port: 2 1
Service: FTP
Description: FTP server opens ports for uploading and downloading. The most common attacker is to find a way to open anonymous's FTP server. These servers have read-write directories. Trojan Doly Trojan, Fore, Stealth FTP, WebEx, WinCrash and blade runner open ports.
Port: 22
Service: Ssh
Description: The connection between TCP established by PcAnywhere and this port may be to find ssh. This service has many weaknesses. If configured in a specific mode, many versions that use the RSAREF library will have many loopholes.
Port: 23
Service: Telnet
Description: Remote login, the intruder is searching for the service of remote login UNIX. In most cases, scanning this port is to find the operating system running on the machine. And using other technologies, intruders will also find the password. Trojan mini Telnet server opens this port.
Port: 25
Service: SMTP
Description: The port opened by SMTP server is used to send mail. Intruders are looking for SMTP servers to send their spam. The intruder's account is closed, and they need to connect to a high-bandwidth email server and send simple information to different addresses. Trojan horse antigen, e-mail password sender, Haebu Coceda, Shtrilitz Stealth, WinPC and WinSpy all open this port.
Port: 80 ......