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# Executing HLA simulation

## CERTI executables

CERTI comes with two main executables: RTIA and RTIG.

### certi_user_execute

If ones want to properly execute an HLA simulation using CERTI one must: (FIXME more detail to come).

1. configure PATH
2. store .fed (or .xml) FOM file in the search path of the rtig
   See also:
     CERTI FOM file search algorithm
3. run rtig,
   See also:
     RTIG
4. configure HOST/PORT/PROXY,
5. run federations, rtia is started automatically.

### CERTI environment variables

CERTI uses a set of environment variables which may influence its execution behavior.

Variable | Used by | Description
CERTI_HOME | RTIG | the CERTI installation base directory. This is used by the RTIG in order to look for FOM files (see RTIG).
CERTI_HOST | RTIA | machine on which RTIG is running. As soon as it starts the RTIA will try to connect to the RTIG running on CERTI_HOST (see RTIA).
CERTI_TCP_PORT | RTIG, RTIA | TCP port used for RTIA/RTIG communications
CERTI_UDP_PORT | RTIG, RTIA | UDP port used for RTIA/RTIG communications
CERTI_HTTP_PROXY | RTIA | HTTP proxy address in the format http://host:port. See HTTP tunneling.
CERTI_NO_STATISTICS | RTIA | if set, do not display service calls statistics

### RTIG: CERTI RunTime Infrastructure Gateway

The CERTI RunTime Infrastructure Gateway (RTIG) is a process which coordinate the HLA simulation with CERTI, there should be at least one rtig process for each federation.

However a single RTIG may be used for several federations. The command line usage of the RTIG is following:

rtig [-v 2]

  - -v (optional) verbosity level
    - 0 -> no output
    - 1 -> small amount
    - 2 -> show fed parse

Once the RTIG is launched an HLA Federate may interact with the RTI. In fact a federate does not talk to the RTIG directly but it uses its RTIA. RTIG is listening to RTIA connection on TCP port:

1. 60400 or,
2. the value of environment variable CERTI_TCP_PORT if it is defined

The RTIG exchange messages with the RTIA in order to satify HLA request coming from the Federate. In particular RTIG is responsible for giving to the Federate (through its RTIA) the FOM file needed to create or join the federation. RTIG tries to open FOM file from different predefined places:.

1. bare filename considered as a path provided through FEDid_name
2. getenv(CERTI_HOME)+"/share/federations"+ FEDid_name
3. default (unix) installation place plus FEDid_name "/usr/local/share/federation/" + FEDid_name

### RTIA: CERTI RunTime Infrastructure Ambassador

The CERTI RunTime Infrastructure Ambassador (RTIA) is a process which is automatically launched by the federate as soon as its RTIambassador is created.

The command line usage of the RTIA is following:

rtia [-v] [-p <port>]

  - -v (optional) verbose, display more information
  - -p (optional) tcp port to be used to communicate with FederateAmbassador

## Sample federate: Billiard

Open a windows command prompt and run the RTIG.

     rtig

Open another windows command prompt and run the billard program.

     billiard -n 1 fTest FTest.fed