--- a/lisp/process.el	Mon Aug 13 11:25:03 2007 +0200
+++ b/lisp/process.el	Mon Aug 13 11:26:11 2007 +0200
@@ -299,7 +299,7 @@
 Remaining arguments are strings to give program as arguments."
   (apply 'start-process-internal name buffer program program-args))
 
-(defun open-network-stream (name buffer host service)
+(defun open-network-stream (name buffer host service &optional protocol)
   "Open a TCP connection for a service to a host.
 Returns a subprocess-object to represent the connection.
 Input and output work as for subprocesses; `delete-process' closes it.
@@ -312,8 +312,18 @@
  with any buffer
 Third arg is name of the host to connect to, or its IP address.
 Fourth arg SERVICE is name of the service desired, or an integer
- specifying a port number to connect to."
-  (open-network-stream-internal name buffer host service))
+ specifying a port number to connect to.
+Fifth argument PROTOCOL is a network protocol.  Currently 'tcp
+ (Transmission Control Protocol) and 'udp (User Datagram Protocol) are
+ supported.  When omitted, 'tcp is assumed.
+
+Ouput via `process-send-string' and input via buffer or filter (see
+`set-process-filter') are stream-oriented.  That means UDP datagrams are
+not guaranteed to be sent and received in discrete packets. (But small
+datagrams around 500 bytes that are not truncated by `process-send-string'
+are usually fine.)  Note further that UDP protocol does not guard against 
+lost packets."
+  (open-network-stream-internal name buffer host service protocol))
 
 (defun shell-quote-argument (argument)
   "Quote an argument for passing as argument to an inferior shell."