update nonblocking methods document.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@10185 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/socket/socket.c

@@ -2286,7 +2286,10 @@ sock_connect(sock, addr)
  * 	  socket.connect_nonblock( sockaddr )
  * 	rescue Errno::EINPROGRESS
  * 	  IO.select(nil, [socket])
- * 	  socket.connect_nonblock( sockaddr )
+ * 	  begin
+ * 	    socket.connect_nonblock( sockaddr )
+ * 	  rescue Errno::EISCONN
+ * 	  end
  * 	end
  * 	socket.write( "GET / HTTP/1.0\r\n\r\n" )
  * 	results = socket.read 
@@ -2623,6 +2626,10 @@ sock_recvfrom(argc, argv, sock)
  * The first element of the results is the data received.
  * The second element contains protocol-specific information
  * on the sender.
+ *
+ * When recvfrom(2) returns 0, Socket#recvfrom_nonblock returns
+ * an empty string as data.
+ * The meaning depends on the socket: EOF on TCP, empty packet on UDP, etc.
  * 
  * === Parameters
  * * +len+ - the number of bytes to receive from the socket
@@ -2745,7 +2752,7 @@ sock_accept(sock)
  * 	socket.listen( 5 )
  * 	begin
  * 	  client_socket, client_sockaddr = socket.accept_nonblock
- * 	rescue Errno::EAGAIN
+ * 	rescue Errno::EAGAIN, Errno::ECONNABORTED, Errno::EPROTO, Errno::EINTR
  * 	  IO.select([socket])
  * 	  retry
  * 	end