JavaBeans Unleashed

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 ...