7.4.2. TCP, UDP Port - Socket

Port, a concept that is an integral part of the functioning of the PC-level of BIOS and hardware, is used here in a completely different purpose. Therefore, the same name but with an entirely different meaning. Port BIOS serves to indicate the direction in which the computer should operate the operating system or program support. So the TCP / IP protocol in its composition contains port, the numerical values based on which the computer for data acquisition means that a service program support (services) must be activated and how to share information. In essence it is about two protocols: TCP and UDP. TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are protocols that ensure the exchange of data between the user's computer, with the port number identifies to which program support (application) of computer data is forwarded. The basic difference between the two is that TCP has control supplies and control errors (ask for a repeat of lost or faulty data packets) and is responsible for the initial establishment of communication between computers, while UDP is much simpler and does not control the exchange of data, and is suitable for communication where errors are allowed (transfer video material). Both protocols for the transfer of user data using the service IP (Internet Protocol), which includes information on the addresses of computers that communicate with each other. Computer gets an IP address as static as the data assigned by the network administrator, or the address of each network access automatically dynamically changes within the range defined by the network administrator. The first method is suitable for workstations and servers within the company, and another for laptop (notebook) or computers using occasional dial-up connection from home.

The numerical value of the port is usually in accordance with the recommendations of the international organization for standardization IANA (Internet Assigned Numbers Authority). Part of the recommendations presented in the following table. With a decade port value shown is the protocol that supports it, and in the following definition and description of the term to which the port concerned.

The table does not show all the port's, but the part most commonly used. Internet content providers sometimes do not use common numbers port's already have some reserved, of course, in consultation with IANA recommendations. Therefore, in the configuration properties of software should write another value if they are not in accordance with the table below. Port allows two concurrent applications or services can interpret the data that were received in the computer, and the IP address of the computer to define who is the data sent and who has them receive. Couple PORT  - IP called SOCKET, end connection points in the communication between the user's computer (animated Figure 7.4.6). The same term is also used to define the type of microprocessor socket and BIOS hardware IRQ address, but then had nothing to do with the method described here. In TCP / IP terminology, it is a connection between two users of the program and the way data exchange between them (TCP or UDP protocol or both), and the name associated with the connection proceeds electrical outlet.

SUMMARY:

General assumptions of Internet access by the users as individuals usually access via dial-up program support OS that provides access through a modem, or other device (ADSL, Cable Modem) connected to an access server of ISP. Then the user does not get a fixed IP Internet address but it is dynamically allocated to it by the access server. Continuous connection to a permanent IP address for individuals is a very expensive solution. Rather, they will use the services of an ISP regarding assigned e-mail addresses and lease part of the disk space of ISP for own web site. Dynamic allocation of IP addresses means that the number of access points to the ISP is less than the total number of users served by the ISP which is occasionally connected to the ISP.

Firms with a larger number of employees mentioned philosophy is not worth it, especially as staff are constantly active and use network resources that are available to them. Local network is the lifeblood of business and corporate communications, and should be given our full attention. How much will be developed and will be able to provide depends on the needs and possibilities of the company. How such a network basically works alone and is a separate part of the overall structure of the Internet is often referred to as an INTRANET, then internal network within a company or institution with an organized approach to the internet thru traffic within the company independently, outside the company and the company. The solutions are very different and principled description of one such network in the following chapter about the Intranet.