PortManager -- Python bindings to port manager


from nscldaq.PortManager import PortManager

pm = PortManager(host, port=30000)

port = pm.getPort(servicename)

portinfo = pm.listPorts()

portinfo = pm.find(key=value,...)


Provides a python interface to the port allocator. The port allocator is a service that runs on NSCLDAQ that allows servicers to obtain a listen port from a pool of dynamically allocated ports. The service is then advertised by the port manager so that clients can locate and connect to the service.


PortManager(string host, int port);

Constructs a PortManager object and returns a reference to it. PortManager objects represent connections to port manager servers. host is the host on which the port manager server is running and port is the port on which the port manager is listening for connections. By default (and if this parameter is not supplied), the port is 30000, which is, by default where the NSCL port manager listens.

The host parameter is a string that can either be the DNS name of the host or the IP address (dotted form) of that host.

int getPort(string servicename);

This method of a port manager object interacts with a local port manager (the host specified whenthe object was created must be localhost) to allocate a port and associated it with a service specification.

Service specification consist of two parts, a service name, specified by the servicname parameter and the name of the user running the server, specified automatically by the getPort method.

On success, the method returns the integer allocated port number. On failure, an exception raised. The exception can be a RuntimeError, if the server reported an error condition, or any other error the socket calls might return.

In the event of a RuntimeError exception, the text of the exception is the error message string returned by the server. Regardless, once an error exception has been raised, the caller should assume that all previously allocated services have been released and that the connection to the port manager object has been terminated. The calling program should allow the port manager object to be garbage collected, and should not attempt to make use of the object again.

list of dicts listPorts();

Obtains a list of the ports the server has allocated. This is most often done to determine which port to perform a socket.connect call on to connect to a specific service. See, however the find which performs some filtering of the full port list obtained via listPorts

The result is a list of dicts. The service key of each dict contains the name of the service, while the user key the user that is running the server. The port key contains the port itself.

list of dicts find(keyword/value list **criteria);

First performs a listPorts call and then filters the data returned by that call using the keyword value pairs in the **criteria.

Keywords are applied cumulatively and in the following order:

service the value of this keyword is a service name that must be exactly matched to allow a port definition to survive the filter.

beginswith is a prefix to the service name. Only services whose names begin with this value survive the filtering. The motivation for this criterion is that if a user starts up more than one service with the same name, the port manager silently appends _n to the name, where n is a unique integer (e.g. myService, myService_1). The prefix criterion allows you to list all instances of a single service run on a node by a user.

user Filters the data to match only those services run by a specific user.