BSD Sockets Programming From A Multi-Language Perspective, Jones, M. Tim

Dan Weeks, 14 November 2003

Introduction

A few weeks ago there was a post on the OpenBSD Journal about a new book on network programming. My interest was piqued as I've done a fair amount of network programming in the past, but I had a desire get back up to speed with it after a hiatus due to moving and changing jobs. With that in mind I ordered BSD Sockets Programming From A Multi-Language Perspective (hereafter referred to as just BSP) so I could refresh my skills.

The generally accepted Application Program Interface (API) for network programming is the BSD Sockets API. This API is available in most programming languages that offer networking and is very similar between most implementations. There are programmers that can go a whole career without ever writing one lick of networking code. This is not a bad thing, but it reflects that while using networked applications is commonplace, developing them isn't necessarily something that every developer will do. However, if a programmer is interested in developing networking code in one of several languages then BSP is probably a good book to start with.

What's Inside

With every book that is trying to introduce a new user to concepts it's best to have clear examples of the subject matter and BSP is no slouch in that department. The book is divided into three sections, an introduction to network programming, sockets programming from a multi-language perspective, and software patterns from a multi-language perspective, giving the user not only a structured experience but also a good set of things they can turn back to in the future when they are utilizing what they've learned.

In part one the networking model and all its layers are clearly explained. Also discussed are Internet protocols, methods of communication, and the model for socket programming. Jones then proceeds to build up sockets piece by piece through code examples. He starts simple, giving the reader all they need to build a network application in perfectly sized chunks. By only giving the user the fundamental parts of socket programming (socket(), bind(), listen(), accept(), etc.) the user is made familiar with the concepts and work flow of a client and a server communicating without getting snowed over by too many details.

Later chapters in part one deal with more advanced topics of network programming. More API calls (gethostbyname(), getsockopt(), setsockopt(), etc.) are discussed that allow the user better control and more choices when creating their applications. The discussion on socket options was particularly clear and enlightening as I was refreshing my knowledge. After making sure the reader has a chance to be well grounded in the sockets API Jones then delves into much more heady topics, but things programmers need to know. Jones presents a lot of good advice on advanced topics, optimizations, and pitfalls that I know I have used or been bitten by in the past.

Part two of BSP is all about actually using socket programming APIs in a variety of languages. The book covers C, Java, Perl, Python, TCL, and Ruby and with each one being it's own chapter it does a good job of binding the socket API from part one to a specific implementation. Each chapter also has a nifty section where the origin and heritage of the language is given.

The third and final part of the book is all about software patterns. Many common topics are discussed including Stream, Datagram, Broadcast, and Multicast clients and servers; a simple web server; and a simple mail server. The strongest point of this section is that each language has it's own chapter and each software pattern is discussed and code given, a definite plus for readers.

The Bottom Line

People that are interested in getting into network programming using BSD sockets need a place to start. BSD Sockets Programming is that place. This book could easily function as a textbook, although it seemed to go very fast for me (however it's been a long while since I've been in class and I already knew network programming going in). Clear wording and not overly complex explanations also help in conveying the subject matter. Many sections of BSP can make for a good reference for the average programmer and having it around so that you could hand to someone that is looking for information is always a plus.

Jones provides excellent code samples (I only found one errata in my read of the entire book, an assignment rather than a comparison in an if statement and the author was very quick and gracious in his reply) and there is an included CD-ROM that has tools and code on it to make it easier to get started. One of the things that impressed me the most was the awesome attention Jones placed on network byte order versus host byte order. He clearly explains the situation and why programmers should care, and then proceeds to hammer the need to make sure data values are in network byte order in a lot of the examples. The only area that could have been better covered is pitfalls with thread programming. There is a brief mention of it at one point in the book, but then there is no mention of either how to determine if parts of the sockets API is thread safe or thread safe alternatives for some of the calls (granted, thread programming is outside the scoop of BSP but even having a reference to some source of thread and network programming would have been cool).

One caveat should be stated here: BSP is for IPv4 programming only. Let me say that again, if you are interested in IPv6 programming you won't find this book useful at all. Now, there are two points to consider here. First, IPv4 is still the prominent mode of networking on the Internet at large. IPv6 just hasn't taken hold yet. Second is that IPv4 is much easier to learn on and there is no reason to cloud a persons learning by throwing multiple IP protocols at them. The W. Richard Stevens book Unix Network Programming, Volume 1 (which Jones references heavily) is a much more appropriate book for IPv6, but it is also a much more heady and complex book for a beginner. For those just starting out with little or no knowledge of network programming BSP is a better choice (then you can step up to the UNPvol1 when you are ready).