USOCKET - Universal socket library for Common Lisp
This is the
usocket Common Lisp sockets library - a library to bring
sockets access to the broadest of Common Lisp implementations as possible.
The library currently supports:
- Allegro CL
- ABCL (ArmedBear)
- Clozure CL
- Corman Lisp
- GNU CLISP
- LispWorks (4.3 and up)
- Digitool MCL and RMCL (5.0 and up)
- Scieneer CL
- Symbolics Lisp Machine (Genera)
If your favorite Common Lisp is missing from the above list, please contact firstname.lastname@example.org and submit a request. Please include references to available sockets functions in your Lisp implementation.
The library is ASDF-enabled, meaning
that you can tar up a checkout and use that to
the package in your system package site. (Or use your usual ASDF
tricks to use the checkout directly.)
Remarks on licensing
Even though the source code has an MIT-style license attached to it, when compiling this code with some of the supported Lisp implementations you may not end up with an MIT-style binary version due to the licensing of the implementations themselves. ECL is such an example and - when it comes to be supported - so is GCL.
Non-support of :external-format
Because of its definition in the Hyperspec, there's no common external-format between Lisp implementations: every vendor has chosen a different way to solve the problem of newline translation or character set recoding.
Because there's no way to avoid platform-specific code in the application
when using external-format, the purpose of a portability layer gets
defeated. So, for now,
usocket doesn't support external-format.
The workaround to get reasonably portable external-format support is to
flexi-streams) on top of a
stream-usocket(class; usocket derivative)
stream-server-usocket(class; usocket derivative)
socket-connect (host port &key element-type)(function)
Create an active/connected socket.
hostcan be a vectorized IP, or a string representation of a dotted IP address, or a hostname for lookup in the DNS system.
socket-listen (host port &key reuseaddress backlog element-type)(function)
Create a passive/listening socket. For possible values of
socket-accept (socket &key element-type)(method)
Create an active/connected socket. Returns (server side) a connected socket derived from a listening/passive socket.
socketis a previously-returned socket.
socket(usocket slot accessor),
Returns the internal/implementation-defined socket representation.
socket-stream (socket)(usocket slot accessor),
Returns a value which satisfies the normal stream interface.
(for a description of the API methods and functions see https://common-lisp.net/project/usocket/api-docs.shtml)
The test suite unfortunately isn't mature enough yet to run without some manual configuration. Several elements are required which are hard to programatically detect. Please adjust the test file before running the tests, for these variables:
+non-existing-host+: The stringified IP address of a host on the same subnet. No physical host may be present.
+unused-local-port+: A port number of a port not in use on the machine the tests run on.
+common-lisp-net+: A vector with 4 integer elements which make up an IP address. This must be the IP "common-lisp.net" resolves to.
CMUCL error reporting wrt sockets raises only simple-errors meaning there's no way to tell different error conditions apart. All errors are mapped to unknown-error on CMUCL.
The ArmedBear backend doesn't do any error mapping (yet). Java defines exceptions at the wrong level (IMO), since the exception reported bears a relation to the function failing, not the actual error that occurred: for example 'Address already in use' (when creating a passive socket) is reported as a
BindExceptionwith an error text of 'Address already in use'. There's no way to sanely map
BindExceptionto a meaningfull error in usocket. [This does not mean the backend should not at least map to
When using the library with ECL, you need the C compiler installed to be able to compile and load the Foreign Function Interface. Not all ECL targets support DFFI yet, so on some targets this would be the case anyway. By depending on this technique, usocket can reuse the FFI code on all platforms (including Windows). This benefit currently outweighs the additional requirement. (hey, it's Embeddable Common Lisp, so, you probably wanted to embed it all along, right?)