package require portAllocator
::portAllocator create name ?-hostname host? ?-port port
::name listPorts
::name findServer service ?user?
::name allocatePort application
::name destroy
The
portAllocator
package provides access to the NSCL TCP/IP port management
server. It can be used by TCP/IP server applications to obtain a server listen
port. The package follows an object oriented model. The application creates
a
portAllocator
object, which stands as a proxy between the application and a
port manager server. Using this object the application can allocated and
deallocate ports, as well as request port allocation information.
Once your application has finished interacting with a
portAllocator object, it
can destroy it. If the application must hold a connection to the server in
order to maintain one or more allocated ports, destruction of the requesting
object will not result in that connection being closed, ensuring that the port will
remain allocated.
Creates a port allocator with the specified name. The optional
-hostname
option allows you to specify with which host you want the
allocator to communicate.
If not supplied, this defaults to localhost. The
optional -port
switch allows you to specify a port on which to connect.
If not specified,the allocator will first attempt to read the port
number from the file
/var/tmp/daqportmgr/listen.port
before falling back
to port number 30000.
The command returns the fully qualified name of the allocator. This name can be stored in a variable for later use (see EXAMPLES).
Returns a TCL formatted list that describes the ports that are currently allocated by the server. Each element of the list is a three element sublist containing in order, the allocated port, the name of the application holding the port, and the name of the user that is running the application.
Finds the port on which a server is listening.
service is the name of the service
advertised by the application and user
if suppled specifiest the user that is running that service.
If not provided, user defaults to that
of the logged in user.
Attempts to allocate a port from the server. Note that the protocol only allows you to allocate ports from a server running on localhost. application is the name of the application under which you would like to register port ownership.
Destroys a portAllocator. If the portAllocator is holding open a connection to the server because the application has allocated a port, this connection will remain open.
The example below allocates a port from the localhost, and starts listening for connections.
Example 1. Allocating a service port in Tcl
package require portAllocator
set p [::portAllocator create local]
set port [$p allocatePort]
socket -server handleConnections $port
The example below requests that the host somehost.nscl.msu.edu return a list of the ports in use. The port usage is then printed at stdout:
Example 2. Listing allocated ports in Tcl
package require portAllocator
set p [::portAllocator create remote -hostname somehost.nscl.msu.edu]
set usage [$p listPorts]
foreach allocation $usage {
set port [lindex $allocation 0]
set application [lindex $allocation 1]
set user [lindex $allocation 2]
puts "Port $port allocated to $application run by $user"
}