Network Clients - Java - page 545

[ 40 ] It used to be universal, when most networked systems were administered by full-time systems
people who had been trained or served an apprenticeship. Today many machines on the Internet don't
have localhost configured properly.
[ 41 ] The UDP packet may need to be fragmented by some networks, but this is not germane to us at the
UDP level, because it will re-assemble the network packets into our “single entity” UDP packet at the
other end.
[ 42 ] When the application doesn't care, these port numbers are usually made up by the operating sys-
tem. For example, when you call a company from a pay phone or cell phone, the company doesn't usu-
ally care what number you are calling from, and if it does, there are ways to find out. Generated port
numbers generally range from 1024 (the first nonprivileged port; see Chapter 16 ) to 65535 (the largest
value that can be held in a 16-bit port number).
[ 43 ] Beware of security holes; don't turn a TFTP server loose on the Internet without first reading a
good security book, such as Building Internet Firewalls , (O'Reilly).
[ 44 ] A thread is one of (possibly) many separate flows of control within a single process; see Running
Code in a Different Thread .
[ 45 ] For an open source program that “AIMs” to let you talk to both from the same program, check out
Jabber at http://www.jabber.org .