# DSRequestMsg

Request message structure.

### Synopsis

    typedef struct DSRequestMsg {
     DS_MSG_HEADER

    union {
     struct {
      DSDataType dataType;
      Item subscriberPort;
      } subscribe;

     struct {
      DSDataType exemptStream;
      unsigned long nowTime;
      } clockSync;

     struct {
      unsigned long markerValue;
      unsigned long options;
      } goMarker;

     struct {
      DSDataType streamType;
      long channelNumber;
      long* channelStatusPtr;
      } getChannel;

     struct {
      DSDataType streamType;
      long channelNumber;
      long channelStatus;
      } setChannel;

     struct {
      DSDataType streamType;
      long userDefinedOpcode;
      void* userDefinedArgPtr;
      } control;

     struct {
      Item acquirePort;
      } connect;

     struct {
      unsigned long options;
      } start;

     struct {
      unsigned long options;
      } stop;

     } msg;

    } DSRequestMsg, *DSRequestMsgPtr

### Description

Messages sent to the streamer by the application to control stream flow and parameters.

### Fields

### subscribe

`dataType`
  4 byte ASCII data type identifier.

`subscriberPort`
  Message port to send data to.

### clockSync

`exemptStream`
  Stream that sync message should not be sent to.

`nowTime`
  Time value to propagate to everyone.

### goMarker

`markerValue`
  Place to "branch" to in the stream.

`options`
  Options for branching.

### getChannel

`streamType`
  Which subscriber.

`channelNumber`
  Logical data channel.

`channelStatusPtr`
  Place to return channel status.

### setChannel

`streamType`
  Which subscriber.

`channelNumber`
  Logical data channel.

`channelStatus`
  Channel status bits to set.

### Control

`streamType`
  Subscriber to send control message to.

`userDefinedOpcode`
  Subscriber defined action code.

`userDefinedArgPtr`
  Subscriber defined argument.

### connect

`acquirePort`
  Connect this data port to stream.

### start

`options`
  Start options.

### stop

`options`
  Stop options.

### Associated Files

DataStream.h