DaqPortManager is a persistent server that should be run at system startup time. The program manages a block of TCP/IP ports. Clients connect to the server to request ports as well as to ask the server to return the current port assignments.
Command options (see OPTIONS) describe how th eprogram starts up. The command options allow the user to define the block of ports that will be managed, to determine which port the port manager itself will listen on for connections and to define where the software will writ its log file. Several other files are maintained by the program (see FILES).
-ports rangeDefines the range of ports that will be managed by the port manager program. This should be specified as a pair of integer number separated by a - (dash). e.g. 30001-31000. If not provided defaults to 30001-31000.
-listen portDefines the port on which the port manager itself will listen for connections. This defaults to 30000. The port manager is itself a server. Most of the software that connects to it assumes the default port will be used to communicate with it, therefore, changing this value will most likely require other changes elsewhere in the NSCLDAQ software
-log logfile
The -log switch is followed by a path to a file
that will be used to
log the server's actions. The server logs connections, port allocations,
port allocation failures, port releases and illegal requests by
clients. The default log file is
/var/log/nscldaq/portmanager.log
-usagefile usagefilename
The
-usagefile
switch is followed by a path to a file that will be used
to hold the instantaneous port usage. This file can be examined to
show the current port usage. Each line in this file is a three element
TCL list of port, application and user for an allocated port. If the
-usagefile switch is not provided, the server defaults to
/var/tmp/daqportmgr/ports.txt.
The server protocol is quite simple. Once connected, two transactions are recognized. Each transaction is requested by the client and fulfilled by the server. Requests are a single line (terminated with a \n) and cann be one of the following:
GIMME requests the server allocate a port. When allocated, the server will believe that the port is allocated to the application named appname run by the user user. If successful, the server replies:
Where the OK indicates success and the portnum is the number of the port allocated.
Indicates a failure where reason is a TCL quoted item describing why the port could not be allocated.
Once a client has allocated a port it must hold a persistent connection to the server. When a client owning ports drops this connection its ports are freed by the server. While possibly inconvenient, this protocol prevents clients from accidently holding on to ports past exit.
Requests that the server list port usage. The server will issue a multiline reply to this request. The first line will be of the form:
Where n is the number of ports that are currently allocated. The n lines that follow each consists of a 3 element TCL list containing in order, the port number, the application name and the name of the user that is running the application. Note that if there are multiple instances of the same application run by the same user, They will be qualified by appending an underscore and an application instance num? ber.
tclsh8.4 /usr/opt/daq/current/bin/DaqPortManager -ports 31000-40000 &
Starts the port manager listening on port 30000 managing ports in the range 31000 through 40000. The port manager is run in the background as a daemon process.
The server maintains:
/var/run/nscldaq/daqportmgr.pid - contains the port manager#033;s process id.
/var/log/nscldaq/portmanager.log - Default logfile
/var/tmp/daqportmgr/listen.port - Contains the listen port for the server.
/var/tmp/daqportmgr/ports.txt - Default port usage file.
The server should be able to default to listen on the service daqportmgr in /etc/services if present before falling back on port 30000
The !uniquification! of the application name for the LIST command may vary from query to query as applications drop out.
Only connections to/from "localhost" are considered local. The server does not bother to determine if any other sources are local even though they may be.
If multiple instances of the port manager are run, only last one started will be listed in /var/run/nscldaq/daqportmgr.pid