Target Communication Framework Services

Copyright (c) 2007 Wind River Systems, Inc. Made available under the EPL v1.0

Direct comments, questions to the mailing list

Table of Contents

Version History

Version Date Change
0.1 2008-01-10 Initial contribution
1.0 2008-05-06 Approved
1.1 2008-06-25 Enhanced error reporting format, see Bug 232410


TCF communication model is based on the idea of services. A service is a group of related commands, events and semantics. For example, Memory Service defines group of command and events for reading and writing target memory. Service definitions are not part of the framework specification, and new services are expected to be defined by developers of tools and target agents. Defenitions of standard services are provided to achieve certain level of compatibility between tools and targets.

Syntax Rules Notation

Format of the protocol messages is defined by syntax rules. Syntax is described using a simple variant of Backus-Naur Form. In particular:

<chars><char><chars> <char>

Error Report Format

Most of TCF standard services use same format for error reporting:

<error report>
    ⇒ null
    ⇒ <object: error description>

Empty or null error report means success. Error description provides error details, including error code and a short, localizable, human readable explanation of the error.

Error description properties are:

"Code" : <integer>
Error code. Can belong to one of predefined ranges:
"Time" : <integer>
Error timestamp, in milliseconds since midnight, January 1, 1970 UTC
"Service" : <string>
Name of the service that reported the error. Required when "Code" is service specific code.
"Format" : <string>
Error description format supports separation between constant and variable parts of error message ("Format" and "Params"). This is done to support localization. Format string is expected to allow translation into foreign languages by means of string table lookup. The format string syntax is defined in the Java language library java.text.MessageFormat. In order to simplify clients written in other languages, only a subset of the syntax is supported:
"Params" : <array>
An array of values to be used together with "Format" to create the error message.
"Severity" : <integer>
Predefined severity values:
"AltCode" : <integer>
Alternative error code. This can be used to represent, for example, OS, POSIX, or other vendor specific error codes
"AltOrg" : <string>
ID of organization defining "AltCode", for example "Linux", "VxWorks", "Wind River", etc
"CausedBy" : <object: error description>
A nested error description. Can be used to describe a root cause of this error.

All fields except "Code" are optional.

Standard error codes:

    OTHER               = 1
    JSON_SYNTAX         = 2
    PROTOCOL            = 3
    CHANNEL_CLOSED      = 5
    UNKNOWN_PEER        = 7
    BASE64              = 8
    EOF                 = 9
    ALREADY_STOPPED     = 10
    ALREADY_EXITED      = 11
    ALREADY_RUNNING     = 12
    IS_RUNNING          = 14
    INV_DATA_SIZE       = 15
    INV_CONTEXT         = 16
    INV_ADDRESS         = 17
    INV_EXPRESSION      = 18
    INV_FORMAT          = 19
    INV_NUMBER          = 20
    INV_DWARF           = 21
    SYM_NOT_FOUND       = 22
    UNSUPPORTED         = 23
    INV_DATA_TYPE       = 24
    INV_COMMAND         = 25

Service specific error code definitions, if any, are part of service specfications. Standard and service specific error codes can be extended over time. A client that does not recognize a specific error code should treat it in the same way as "OTHER".

For encoding of <object>, <string>, etc., see JSON - Preferred Marshaling.