Real World Haskell

Chapter 27. Sockets and Syslog

Basic Networking

In several earlier chapters of this book, we discussed services that operate over a network. Two examples are client/server databases and web services. When the need arises to devise a new protocol or to communicate with a protocol that doesn’t have an existing helper library in Haskell, you’ll need to use the lower-level networking tools in the Haskell library.

In this chapter, we will discuss these lower-level tools. Network communication is a broad topic with entire books devoted to it. We will show you how to use Haskell to apply the low-level network knowledge you already have.

Haskell’s networking functions almost always correspond directly to familiar C function calls. As most other languages also layer on top of C, you should find this interface familiar.

Communicating with UDP

UDP breaks data down into packets. It does not ensure that the data reaches its destination or it reaches it only once. It does use checksumming to ensure that packets that arrive have not been corrupted. UDP tends to be used in applications that are performance- or latency-sensitive, in which each individual packet of data is less important than the overall performance of the system. It may also be used where the TCP behavior isn’t the most efficient, such as ones that send short, discrete messages. Examples of systems that tend to use UDP include audio and video conferencing, time synchronization, network-based filesystems, and logging systems.

UDP Client ...