Socket#accept no such method?

The reason we have never implemented this is because the JDK separates server from client sockets at construct time. We can't open a socket first and then decide it will act as a server later. We must make that decision when we construct the object that actually opens up an fd.

The question for me has always been this: why can't a user decide that it's a ServerSocket when they're opening it?

I'll poke around and see if anything has changed in the JDK APIs we use, but that's the short story.

More concrete pointers...

At socket create time, we need to either create one of these:

http://docs.oracle.com/javase/6/docs/api/java/nio/channels/SocketChannel.html

or one of these:

http://docs.oracle.com/javase/6/docs/api/java/nio/channels/ServerSocketChannel.html

At one point we debated possibly deferring the creation of the actual channel until the user picks connect or accept, but then we're not actually allocating the fd, can't set flags, etc. It becomes pretty message to defer the creation, since a lot of other pre-connect/accept methods still need to work, and may cause us to force it into existence before we know if it will do a connect or an accept.

Ok, I have a workaround I'm considering shipping with JRuby 1.7. I added "ServerSocket".

The logic is pretty much the same as for using Socket like you want, but instead you'd use ServerSocket and it will have an "accept" method. It's a simple change for your code, and to make it compatible with MRI you can just set ServerSocket = Socket.

Does that sound reasonable?

Ok, I added ServerSocket on master in the folllowing commit. I'd appreciate you giving it a shot, and I'll look into whether existing tests can be used to confirm it's functioning properly (may be hard since they all use Socket and not ServerSocket).

commit d5a87bf2d6e8458ba0c0e35149ab0132d576efe9
Author: Charles Oliver Nutter <headius@headius.com>
Date:   Tue Mar 6 16:21:48 2012 -0600

    Fix JRUBY-6526 and continue socket refactoring.
    
    * Moved most Socket class methods to SocketUtils
    * Added ServerSocket as a JRuby workaround for Socket only being clients
    * Added support for symbolic domain, type, and protocol (1.9)
    * Added 1.9 Socket#initialize with two args

FWIW, the shortest-term workaround is to just use TCPServer when you need a server.

To make it easier for others to find ServerSocket in the future, I've added an #accept impl to Socket that just errors and points users to ServerSocket at http://wiki.jruby.org/ServerSocket.

commit 7fb8ea02a5292b6a64de218253b756e1c14c61fb
Author: Charles Oliver Nutter <headius@headius.com>
Date:   Tue Mar 6 23:44:50 2012 -0600

    Add error message for Socket#accept.
    
    Because we can't support both client and server connections in
    Socket, we have added ServerSocket for the server side. To make
    this easier to find, I've added an impl of Socket#accept that
    mentions ServerSocket and links to an informational page on the
    JRuby wiki.

Marking this resolved. We can't support #accept directly on Socket, but I think the ServerSocket class is a pretty good workaround.