Ubuntu Manpage: ams - CCSDS Asynchronous Message Service(AMS) communications library

NAME

       ams - CCSDS Asynchronous Message Service(AMS) communications library

SYNOPSIS

           #include "ams.h"

           typedef void                (*AmsMsgHandler)(AmsModule module,
                                               void *userData,
                                               AmsEvent *eventRef,
                                               int continuumNbr,
                                               int unitNbr,
                                               int moduleNbr,
                                               int subjectNbr,
                                               int contentLength,
                                               char *content,
                                               int context,
                                               AmsMsgType msgType,
                                               int priority,
                                               unsigned char flowLabel);

           typedef void                (*AmsRegistrationHandler)(AmsModule module,
                                               void *userData,
                                               AmsEvent *eventRef,
                                               int unitNbr,
                                               int moduleNbr,
                                               int roleNbr);

           typedef void                (*AmsUnregistrationHandler)(AmsModule module,
                                               void *userData,
                                               AmsEvent *eventRef,
                                               int unitNbr,
                                               int moduleNbr);

           typedef void                (*AmsInvitationHandler)(AmsModule module,
                                               void *userData,
                                               AmsEvent *eventRef,
                                               int unitNbr,
                                               int moduleNbr,
                                               int domainRoleNbr,
                                               int domainContinuumNbr,
                                               int domainUnitNbr,
                                               int subjectNbr,
                                               int priority,
                                               unsigned char flowLabel,
                                               AmsSequence sequence,
                                               AmsDiligence diligence);

           typedef void                (*AmsDisinvitationHandler)(AmsModule module,
                                               void *userData,
                                               AmsEvent *eventRef,
                                               int unitNbr,
                                               int moduleNbr,
                                               int domainRoleNbr,
                                               int domainContinuumNbr,
                                               int domainUnitNbr,
                                               int subjectNbr);

           typedef void                (*AmsSubscriptionHandler)(AmsModule module,
                                               void *userData,
                                               AmsEvent *eventRef,
                                               int unitNbr,
                                               int moduleNbr,
                                               int domainRoleNbr,
                                               int domainContinuumNbr,
                                               int domainUnitNbr,
                                               int subjectNbr,
                                               int priority,
                                               unsigned char flowLabel,
                                               AmsSequence sequence,
                                               AmsDiligence diligence);

           typedef void                (*AmsUnsubscriptionHandler)(AmsModule module,
                                               void *userData,
                                               AmsEvent *eventRef,
                                               int unitNbr,
                                               int moduleNbr,
                                               int domainRoleNbr,
                                               int domainContinuumNbr,
                                               int domainUnitNbr,
                                               int subjectNbr);

           typedef void                (*AmsUserEventHandler)(AmsModule module,
                                               void *userData,
                                               AmsEvent *eventRef,
                                               int code,
                                               int dataLength,
                                               char *data);

           typedef void                (*AmsMgtErrHandler)(void *userData,
                                               AmsEvent *eventRef);

           typedef struct
           {
               AmsMsgHandler                   msgHandler;
               void                            *msgHandlerUserData;
               AmsRegistrationHandler          registrationHandler;
               void                            *registrationHandlerUserData;
               AmsUnregistrationHandler        unregistrationHandler;
               void                            *unregistrationHandlerUserData;
               AmsInvitationHandler            invitationHandler;
               void                            *invitationHandlerUserData;
               AmsDisinvitationHandler         disinvitationHandler;
               void                            *disinvitationHandlerUserData;
               AmsSubscriptionHandler          subscriptionHandler;
               void                            *subscriptionHandlerUserData;
               AmsUnsubscriptionHandler        unsubscriptionHandler;
               void                            *unsubscriptionHandlerUserData;
               AmsUserEventHandler             userEventHandler;
               void                            *userEventHandlerUserData;
               AmsMgtErrHandler                errHandler;
               void                            *errHandlerUserData;
           } AmsEventMgt;

           typedef enum
           {
               AmsArrivalOrder = 0,
               AmsTransmissionOrder
           } AmsSequence;

           typedef enum
           {
               AmsBestEffort = 0,
               AmsAssured
           } AmsDiligence;

           typedef enum
           {
               AmsRegistrationState,
               AmsInvitationState,
               AmsSubscriptionState
           } AmsStateType;

           typedef enum
           {
               AmsStateBegins = 1,
               AmsStateEnds
           } AmsChangeType;

           typedef enum
           {
               AmsMsgUnary = 0,
               AmsMsgQuery,
               AmsMsgReply,
               AmsMsgNone
           } AmsMsgType;

           [see description for available functions]

DESCRIPTION

The ams library provides functions enabling application software to use AMS to send and
receive brief messages, up to 65000 bytes in length. It conforms to AMS Blue Book,
including support for Remote AMS (RAMS).

In the ION implementation of RAMS, the "RAMS network protocol" may be either the DTN
Bundle Protocol (RFC 5050) or -- mainly for testing purposes -- the User Datagram Protocol
(RFC 768). BP is the default. When BP is used as the RAMS network protocol, endpoints
are by default assumed to conform to the "ipn" endpoint identifier scheme with node number
set to the AMS continuum number and service number set to the AMS venture number.

Note that RAMS functionality is enabled by instantiating a ramsgate daemon, which is
simply an AMS application program that acts as a gateway between the local AMS message
space and the RAMS network.

AMS differs from other ION packages in that there is no utilization of non-volatile
storage (aside from the BP functionality in RAMS, if applicable). Since there is no non-
volatile AMS database, there is no AMS administration program and there are no library
functions for attaching to or detaching from such a database. AMS is instantiated by
commencing operation of the AMS real-time daemon amsd; once amsd is running, AMS
application programs ("modules") can be started. All management of AMS operational state
is performed automatically in real time.

However, amsd and the AMS application programs all require access to a common store of
configuration data at startup in order to load their Management Information Bases. This
configuration data must reside in a readable file, which may take either of two forms: a
file of XML statements conforming to the scheme described in the amsxml(5) man page, or a
file of simple but less powerful configuration statements as described in the amsrc(5) man
page. The amsxml alternative requires that the expat XML parsing system be installed; the
amsrc alternative was developed to simplify deployment of AMS in environments in which
expat is not readily supported. Selection of the configuration file format is a compile-
time decision, implemented by setting (or not setting) the -DNOEXPAT compiler option.

The path name of the applicable configuration file may be passed as a command-line
parameter to amsd and as a registration function parameter by any AMS application program.
Note, though, that ramsgate and the AMS test and utility programs included in ION always
assume that the configuration file resides in the current working directory and that it is
named "mib.amsrc" if AMS was built with -DNOEXPAT, "amsmib.xml" otherwise.

The transport services that are made available to AMS communicating entities are declared
by the transportServiceLoaders array in the libams.c source file. This array is fixed at
compile time. The order of preference of the transport services in the array is hard-
coded, but the inclusion or omission of individual transport services is controlled by
setting compiler options. The "udp" transport service -- nominally the most preferred
because it imposes the least processing and transmission overhead -- is included by
setting the -DUDPTS option. The "dgr" service is included by setting the -DDGRTS option.
The "vmq" (VxWorks message queue) service, supported only on VxWorks, is included by
setting the -DVMQTS option. The "tcp" transport service -- selected only when its quality
of service is required -- is included by setting the -DTCPTS option.

The operating state of any single AMS application program is managed in an opaque
AmsModule object. This object is returned when the application begins AMS operations
(that is, registers) and must be provided as an argument to most AMS functions.

int ams_register(char *mibSource, char *tsorder, char *applicationName, char
*authorityName, char *unitName, char *roleName, AmsModule *module)
Registers the application within a cell (identified by unitName) of a message space
that is that portion of the venture identified by applicationName and authorityName
that runs within the local AMS continuum. roleName identifies the role that this
application will perform in this venture. The operating state of the registered
application is returned in module.

The application module's identifying parameters are validated against the
configuration information in the applicable Management Information Base, which is
automatically loaded from the file whose pathname is provided in mibSource. If
mibSource is the zero-length string ("") then the default configuration file name is
used as noted above. If mibSource is NULL then a rudimentary hard-coded default MIB,
useful for basic testing purposes, is loaded. This default MIB defines a single
venture for application "amsdemo" and authority "test", using only the "dgr" transport
service, with the configuration server residing on the local host machine; subject
"text" and roles "shell", "log", "pitch", and "catch" are defined.

The tsorder argument is normally NULL. If non-NULL it must be a NULL-terminated
string of ASCII numeric digits '0' through '9' identifying an alternative transport
service preference order that overrides the standard transport service preference
order defined by the hard-coded array of transportServiceLoaders in the libams.c
source file. Each character of the tsorder string must represent the index position
of one of the transport services within the array. For example, if services "udp",
"dgr", "vmq", and "tcp" are all available in the array, a tsorder string of "32" would
indicate that this application will only communicate using the tcp and vmq services;
services 0 (udp) and 1 (dgr) will not be used, and tcp is preferred to vmq when both
are candidate services for transmission of a given message.

Returns 0 on success. On any error, sets module to NULL and returns -1.

int ams_unregister(AmsModule module)
Reverses the operation of ams_unregister(), destroying module. Returns 0 on success,
-1 on any error.

int ams_invite(AmsModule module, int roleNbr, int continuumNbr, int unitNbr, int
subjectNbr, int priority, unsigned char flowLabel, AmsSequence sequence, AmsDiligence
diligence)
Announces this module's agreement to receive messages on the subject identified by
subjectNbr.

The invitation is extended only to modules registered in the role identified by
roleNbr (where 0 indicates "all roles"), operating in the continuum identifed by
continuumNbr (where 0 indicates "all continua"), and registered within the unit
identified by unitNbr (where 0 indicates the venture's root unit) or any of that
unit's subunits. These parameters define the "domain" of the invitation.

Such messages should be sent at the priority indicated by priority with flow label as
indicated by flowLabel and with quality of service as indicated by sequence and
diligence. priority must be an integer in the range 1-15, where priority 1 indicates
the greatest urgency. Flow labels are passed through to transport services and are
opaque to AMS itself; in the absence of defined flow labels, a value of 0 is typically
used. These parameters define the "class of service" of the invitation.