Start listening range at 1024 instead of 1

Avoid privileged ports by default

Closes #651

net.go

@@ -106,7 +106,7 @@ func listenUDPInPortRange(n transport.Net, log logging.LeveledLogger, portMax, p
 	var i, j int
 	i = portMin
 	if i == 0 {
-		i = 1
+		i = 1024 // Start at 1024 which is non-privileged
 	}
 	j = portMax
 	if j == 0 {