Introduction to several operational logic of C language

MTU: Communication term Maximum Transmission unit (Maximum transmission UNIT,MTU) is the maximum packet size (in bytes) that can be passed on a layer of a communication protocol. Maximum Transmission Unit This parameter is usually related to the communication Interface (network interface card, serial port, etc.).

The Chinese name of the VLAN (virtual local area network) is a "virtualized LAN". VLAN is a kind of new data exchange technology which divides LAN device into network segment logically and realizes virtual workgroup.

The WLAN (Wireless Local area Networks;wlan) is a fairly convenient data transmission system that utilizes the technology of radio frequency (Radio FREQUENCY;RF) to replace the local-area network of old-fashioned stranded copper (Coaxial). The wireless local area network can make use of the simple access architecture to let the user through it, achieves "the information carries on, the convenience walks the world" the ideal realm.

Virtual private network (VPN private network) refers to the technology of establishing a private network on a public network. It is called a virtual network, the main reason is that the connection between any two nodes of the entire VPN network does not have the End-to-end physical link required by the traditional private network, but the network platform provided by the public service provider, such as the Internet, ATM (asynchronous transfer Mode), frame Relay (frames Relay And so on, the user data is transmitted in the logical link. It covers extensions of private networks that encapsulate, encrypt, and authenticate links across shared networks or public networks. The VPN mainly uses the color tunneling technology, encryption and decryption technology, key management technology and user and equipment identity authentication technology.

The Network layer---Packet format there is a very important field called the protocol number. For example, in the transport layer if the TCP connection, then the network layer IP packet inside the protocol number will have a value of 6, if it is UDP the value is---transport layer.

The Transport layer------the application layer through an interface association (the port's field is called a port).

Use Netstat–an to view the port number that is open on this machine.

Proxy servers use the following ports:

(1), HTTP protocol proxy Server common port number: 80/8080/3128/8081/9080

(2), SOCKS Proxy Protocol server common port number: 1080

(3), FTP (file Transfer) protocol Proxy Server Common port number: 21

(4), Telnet (telnet) protocol proxy Server common port: 23

HTTP server, the default port number is 80/tcp (Trojan executor open this port);

HTTPS (securely transferring Web pages) server, the default port number is 443/TCP 443/udp;

Telnet (unsecured text transfer), the default port number is 23/tcp (a Trojan tiny a port opened by Telnet server);

FTP, the default port number is 21/tcp (Trojans Doly Trojan, Fore, invisible FTP, WebEx, Wincrash, and Blade Runner open ports);

TFTP (Trivial File Transfer Protocol), the default port number is 69/UDP;

SSH (Secure login), SCP (file transfer), port redirection, the default port number is 22/tcp;

SMTP Simple Mail Transfer Protocol (e-mail), the default port number is 25/tcp (Trojan antigen, Email Password Sender, Haebu Coceda, Shtrilitz Stealth, WINPC, Winspy are all open this port);

POP3 Post Office Protocol (e-mail), the default port number is 110/tcp;

WebLogic, the default port number is 7001;

Webshpere application, the default port number is 9080;

Webshpere management tool, the default port number is 9090;

JBOSS, the default port number is 8080;

TOMCAT, the default port number is 8080;

WIN2003 remote login, the default port number is 3389;

Symantec Av/filter for MSE, the default port number is 8081;

Oracle database, the default port number is 1521;

ORACLE Emctl, the default port number is 1158;

Oracle XDB (XML database) with the default port number of 8080;

Oracle XDB FTP service with the default port number of 2100;

MS sql*server database server, the default port number is 1433/TCP 1433/udp;

MS sql*server Database Monitor, the default port number is 1434/TCP 1434/udp;

QQ, the default port number is 1080/UDP.