:SOCKETS

This is a package for SBCL which implements a lot of what is commonly known as the BSD sockets API, as FFI calls to the C library. I don't know what the exact scope of "BSD sockets" is, but I've taken all the bits that make sense. Development and testing thus far has mostly been done on ix86 and Alpha GNU/Linux; feedback from users of other platforms is solicited

Current status

Mon Jan 7 23:33:46 GMT 2002 version 0.5 supports the "file" (a.k.a. unix) domain for sockets, as well as a bundle of other fixes. Get it from cCLan

Sun Jan 7 01:48:37 GMT 2001 version 0.41 (first of the new millennium) is mostly bugfixes and updates to make it work with more recent SBCL versions. User-visible change: SOCKET-ERROR conditions now have ERROR rather than CONDITION as superclass

Mon Jul 3 17:09:16 BST 2000 version 0.4 has more portability fixes (now runs on Solaris with CMUCL, and may work on FreeBSD with SBCL), and returns more meaningful error messages for name service errors. Thanks to Brad Chapman for FreeBSD, Eric Marsden (Solaris), Graham Ward (name service), and my employers for keeping Sparc boxes around that still run Solaris. Linux/Alpha in 0.4.x one day soon

Sat May 20 18:28:21 BST 2000 version 0.3.7b has no functional changes, but thanks to patches from Martin Atzmueller should build more cleanly on SBCL.

Thu May 11 00:51:21 BST 2000 version 0.3.6 lets you set non-blocking mode on a socket.

Mon May 1 02:29:42 BST 2000 version 0.3.5 corrects a nasty bug in the CMUCL version. If you're running 0.3 (and I know you're not, so don't pretend) you will almost certainly want to upgrade

Mon Apr 17 19:22:32 BST 2000 version 0.3 released; get it at sockets-0.3.tar.gz. Changes -

• Now works with SBCL (0.6.1, 0.6.2) in addition to CMUCL.
• Fixed to actually work with a READ-SEQUENCE implementation that does the right thing instead of the (suspected buggy) implementation in CMUCL. At least, the Hyperspec doesn't give me any particular cause for belief that READ-SEQUENCE can return before reading as much as the user asks it to, which is what we were using it for hitherto.
• The Makefile got a lot bigger. defs-to-lisp.lisp got a lot smaller.
• Standard make target creates "sockets-system.x86f" which contains all the code in a single file

If you want to build it on SBCL you'll need a working defsystem for said platform first. This involves some fiddling around: first you need to get it from CLOCC on Sourceforge then you need to patch it with this diff. Unless you're looking at a version newer than 1.12, in which case they might have patched it already before you got to it.

As of Sat Mar 25 15:54:51 GMT 2000, the system exists to the extent that TCP clients and servers can both be implemented, but its only real advantage over the CMUCL code is the ability to set SO_REUSEADDR. Development directions actively being pursued right now can be seen by looking at the TODO file

Implementation continues. You can find a window onto the current CVS repository at http://loaclhost.telent.net/cgi-bin/cvsweb/telent/sockets, and often an update of what's changed lately at http://www.advogato.org/person/dan/

Motivation

The motive behind developing another sockets support library is twofold:

• I wish to have the full flexibility of the C interface available from a sensible language. To take a fairly commonly-used example, the existing CMUCL code does not, for example, allow a server to set the socket option SO_REUSEADDR - this is essential for stopping and quickly restarting a server on the same port (e.g. a web server) and additionally its lack will drive a developer crazy quite fast during development. Other features which I wish to be able to support include UDP servers, querying the path MTU, toggling the Nagle algorithm and so on
• SBCL (a new free Common Lisp born of CMUCL) has the same foreign function interface as CMUCL, but no socket library at all. I hope that this system will fill the gap for people who need same.

Design Principles

The initial ideas for API design were provided by Perl's IO::Socket functions, but the perspective shifted somewhat during design; we ended up probably nearer the C API than the Perl one. So:

• Each major function in :SOCKETS corresponds to a function in the BSD socket API. This makes the system manual pages useful when coding in Lisp.
• The worst excesses of type punning in the C API have been removed. Integers "in network byte order", for example, have been replaced with vectors of (unsigned 8) to make it clear that we're talking about a sequence of bytes.
• The code uses a clean design that allows it not to be cluttered with #+foo directives for different platforms. It gets structure layouts and symbolic constants from a C program which must be built and run at installation time.
• Error handling is uniformly handled using the Common Lisp condition system. If any of the underlying socket calls returns indicating that an error happened, a condition whose supertype is SOCKET-ERROR is thrown. The exact condition type depends on the error returned; there is intended to be one condition per interesting errno value.