Connection

Warning

This page contains features that are unfinished, were never implemented, or have since been deprecated. We preserve these pages for archival purposes, and also as a foundational resource for prospective developers who may wish to implement the same or similar feature. Many of these pages provide robust explanations of the theory behind a particular module or feature that we hope readers will find useful.

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The client/server connection module implements a common set of data exchange and co-simulation links for both clients and servers. Various underlying transport protocols are supported and various data format protocols are implemented by the classes of objects. A common security model is shared by all the interfaces ensuring that all external interactions are managed consistently across all the various connection types.

Synopsis

module connection {
  security NONE|LOW|NORMAL|HIGH|EXTREME;
  lockout 10 s;
}

Classes

Each class joins three basic characteristics of a connection:

  • whether the connection mode is SERVER or CLIENT,
  • whether the connection transport is UDP or TCP, and
  • the data exchange protocol supported by the connection.

The data exchange protocol determines the name of the class. The follow classes (hence protocols) are proposed (italics) or supported (bold):

  • xml: implements XML links
  • json: implements JSON links
  • fncs_msg: implements FNCS library for FNCS co-simulations.
  • helics_msg: implements the HELICS library for HELICS co-simulations.
  • gridlabd: implements gridlabd links
  • volttron: implements volttron links
  • matlab: implements matlab links

The connection mode and transport are properties of the underlying class from which all connection classes are derived.

Example

The following example sets up a simple XML server 

module connection 
{
   security STANDARD;
}
class xml 
{
   mode SERVER; // enable server mode
   transport TCP; // use TCP for data transport
   from 127.0.0.1; // only accept incoming connections from the local host
   port 8080; // use port 8080 
   version 1.0; // use XML version 1.0
   encoding UTF8; // use 8bit character encoding
   schema "<http://www.gridlabd.org/gridlabd_3.0.xsd>"; // use 3.0 schema
   stylesheet "<http://www.gridlabd.org/gridlabd_3.0.xsl>"; // use 3.0 stylesheet
   security HIGH; // override default module security
   link "file:datamap.txt"; // datalink map from file (allows external link command lists);
   link "allow:local_object.var1 -> remote_1"; // permit data send
   link "forbid:local_object.var2 <- remote_2"; // forbid data receive
   link "presync:local_object.var3 -> remote_3"; // force data send on precommit, presync, sync, postsync, commit, or finalize
}