Chapter 4. Net


In the previous chapters, you've looked extensively at HTTP and HTMLtwo of the most fundamental standards behind the Internet. The major protocols behind email (POP3, SMTP, IMAP, MIME) are all supported by JavaMail (http://java.sun.com/products/javamail/). This leaves a tremendous number of other protocols, however.

The Jakarta Commons Net package covers a huge number of the other standard Internet protocols, including Finger, Whois, TFTP, Telnet, FTP, NNTP, and some miscellaneous protocols such as Time, Echo, and BSD R. POP3 and SMTP are also supported, but JavaMail (http://java.sun.com/products/javamail/) provides a more mainstream, higher-level wrapper for these protocols.

Finger http://www.faqs.org/rfcs/rfc742.html. A simple status inquiry.

Whois http://www.faqs.org/rfcs/rfc954.html. A lookup mechanism, allowing users to find information about registered users (in particular, used by domain name registries, such as Network Solutions, http://www.networksolutions.com/en_US/whois/index.jhtml).

TFTP http://www.faqs.org/rfcs/rfc991.html. A very simple file transfer protocol with no access control. Sometimes found on local networks as part of a network boot process.

Telnet http://www.faqs.org/rfcs/rfc854.html. A generic two-way protocol, most commonly used for remote shell access, but also acting as the underlying infrastructure of other standards (such as FTP).

FTP http://www.faqs.org/rfcs/rfc959.html. A popular, more sophisticated file transfer protocol than TFTP.

NNTP http://www.faqs.org/rfcs/rfc977.html. Network News Transfer Protocol, most popularly known as the underlying protocol behind USENET. If you aren't familiar with USENET, check the Google interface available at http://www.google.com/grphp.

BSD "R" Commands A set of commands intended to provide remote services without a login (including rexec, rcmd/rshell, and rlogin). For more information (including a discussion of the security implications), see http://www.busan.edu/~nic/networking/firewall/ch08_04.htm.

Warning:

It should be noted that virtually no security is built into any of these protocols. Those that offer username/password authentication transfer login information in the clear. If you are interested in secure alternatives, you may want to consider a virtual private network or the use of an SSH tunneling system such as OpenSSH (http://www.openssh.org/).


This chapter will first look at the overall architecture of the Net package and then delve more deeply into the FTP and NNTP clients.



    Apache Jakarta Commons(c) Reusable Java Components
    Real World Web Services
    ISBN: N/A
    EAN: 2147483647
    Year: 2006
    Pages: 137
    Authors: Will Iverson

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