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JavaBeans Unleashed by Rick Leinecker, Dr. Donald Doherty

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Using Network Services

TCP/IP networks provide a variety of network services through their Application layer protocols. Network services include electronic mail, Telnet for remote logon, and File Transfer Protocol (FTP) for transferring files across networks.

Each network service is associated with a port. A port is a logical number assigned to a particular service through which the service is requested. Some network services and their common port numbers are listed in Table 16.1.

Table 16.1. Network Services
Service Port Description
FTP Data 20 File Transfer Protocol data
FTP Control 21 File Transfer Protocol commands
Telnet 23 Telnet remote logon
SMTP 25 Simple Mail Transfer Protocol
DNS 53 Domain Name Server
TFTP 69 Trivial File Transfer Protocol ...

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