Am 09.03.2012 um 18:44 schrieb Sven Van Caekenberghe: > > On 09 Mar 2012, at 16:56, Philippe Marschall wrote: > >> On 03/09/2012 04:44 PM, Sven Van Caekenberghe wrote: >>> Most socket API's allow for the creation of a server socket on the next >>> available port, often by specifying 0 instead of a port. When the socket is >>> bound, one can retrieve the local port and let the client(s) know. I tried >>> to do that in Pharo today, and these steps seem to work, by accepting an >>> incoming connection gives a primitive failed. >> >> Stupid n00b question, isn't 0 a valid port number? > > I don't think so, in Java: > > http://docs.oracle.com/javase/1.4.2/docs/api/java/net/ServerSocket.html#ServerSocket() > > ServerSocket > > public ServerSocket (int port) throws IOException > > Creates a server socket, bound to the specified port. A port of 0 creates a > socket on any free port. > Well, I think it is sort of a definition thing. From the protocol perspective 0 is a valid port number in the priviledged segment (0-1023). But reservation of services is done via IANA and there port 0 is "reserved" for UDP and TCP. For your own services you usually wouldn't choose a reserved port numbe like 80,22,etc. That makes 0 kind of free for intermediate use :)
Norbert
