Understanding Message Objects
So far, we have seen that subscribing to a topic involves working with
objects of type AMPS.Client.Message. A Message represents a
single message to or from an AMPS server. Messages are received or sent
for every client/server operation in AMPS.
Header Properties
There are two parts of each message in AMPS: a set of headers that
provide metadata for the message, and the data that the message
contains. Every AMPS message has one or more header fields defined. The
precise headers present depend on the type and context of the message.
There are many possible fields in any given message, but only a few are
used for any given message. For each header field, the Message class
contains a distinct property that allows for retrieval and setting of
that field. For example, the Message.getCommandId() function
corresponds to the commandId header field, the
Message.getBatchSize() function corresponds to the BatchSize
header field, and so on. For more information on these header fields,
consult the AMPS User Guide and AMPS Command Reference.
To work with header fields, a Message contains
getXxx()/setXxx() methods corresponding to the header fields.
60East does not recommend attempting to parse header fields from the raw
data of the message.
In AMPS, fields sometimes need to be set to a unique identifier value.
For example, when creating a new subscription, or sending a manually
constructed message, you’ll need to assign a new unique identifier to
multiple fields such as CommandId and SubscriptionId. For this
purpose, Message provides newXxx() methods for each field that
generates a new unique identifier and sets the field to that new value.
Data Property
Access to the data section of a message is provided via the Data
property. The Data property will contain the unparsed data of the
message. The Data property returns the data as a .Net string, which
is suitable for message formats that can be represented as Unicode text,
such as JSON, XML, FIX, or NVFIX. For binary data, the AMPS C# client
provides a getDataRaw() method to allow you to work with the
underlying byte array in the message. See the section on
Byte Buffers
for details.
The AMPS C# client contains a collection of helper classes for working with message types that are specific to AMPS (for example, FIX, NVFIX, and AMPS composite message types). For message types that are widely used, such as JSON or XML, you can use whichever library you typically use in your environment.
Message Field Reference
The AMPS Command Reference contains a full description of which fields are available and which fields are returned in response to specific commands.