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The PC World explains what ports and port scanner such as Nmap, as you discover vulnerabilities including Nmap and protect themselves against attackers.
Each PC requires open ports for Internet, Mail and Messenger. For ports, the input and output ports of your computer and Dell latitude d630 battery , any Internet-related applications are an open port required. But open ports are potential gateways for attackers. Moreover, important for the in-depth understanding of firewalls knowledge of ports.
The lion's share of Internet communication is done via the TCP and UDP protocols, so for example, the Internet traffic that is going on in your browser or mail program. Any application that is connected to the Internet in connection point to the TCP and UDP port number. So "" knows every data packet, to which application it belongs, so to speak, the port is the address for a particular type of Internet data. A HTTP packet for the browser ends up not in the mail program and a package of mail found its way into your mail client and not end up in the browser, thanks to each packet reaches its correct destination port numbers.
Sockets are the addresses of PCs and servers
Completing the address of a data packet with the IP address of the target Rechnerns. The combination of IP address of the target host and port number of the target application on the target machine is called a socket. Two sockets define a connection, one for the output and one for the target computer and latitude d620 battery . Thanks to the socket of each data Pact lands on the correct computer in the correct application. Conversely, there are of course on the server that makes the data available, the sockets, that is: There, too, have the appropriate ports open. Which brings us back to the subject would be.
Responsible for incoming mail POP3 server is working for example on port 110, a web server listening on port 80 (if you run even a web server on your computer, you have this when commissioning a port. Default is 80, is there an other its port (because you run two web servers simultaneously, for example), you must explicitly specify the way such as Apache's configuration file).
Each data packet therefore knows which port it is addressed. For this he is in fact added to the header of the data segment the sender and the destination port number. This applies to both the TCP and UDP for the protocol.
Server processes are always static port numbers, client requests get assigned to every request against a dynamic port number. A unique socket for a request to a web server (as are the open source Apache or Internet Information Services IIS from Microsoft) with the IP address 192.168.1.18 might look as follows: 192.168.1.18:80. And if the requesting client computer's IP address 192.168.100.12 has, then the socket for the supplied site would look like this: 192.168.100.12:49152 - whereby the latter would be the dynamically allocated port for the answer.