Detailed Description

The Transport is a class used to simplify the handling of configurable communication in an IOServer. It provides methods to configure itself from XML, and it has functions to Read() and Write() data.

Usage

The Transport is typically created from the Component HandleXMLElement function:

#include <IO/Transport.h>
...
bool CustomIO::HandleXMLElement(XMLElementEx* pEx)
{
  if (pEx->GetName()=="Transport")
  {
    m_transport = CDP::IO::Transport::Create(pEx,m_parent);
    if (m_transport==nullptr)
      Suspend();
    else
      m_transport->Configure(pEx,this);
    return true;
  }
  return IOServer::HandleXMLElement(pEx); // call base
}

The above code will cause the component to make one of the supported transport layers when they are encountered in the configuration.

To add a Transport table to a model, in Configure mode:

• Add a CDPModel -> AggregateBaseModel
• In the Elements table, rename AggregateBaseModel to Transport
• Set the Transport AcceptsBase column value to Transport to accept Transport models.
• Build the library to apply the changes; a table named Transport should now appear in your model.

To add a preconfigured UDP tranport to your model, in Configure mode, add a CDPCore -> UDPTransport. You can then pre-configure the transport by going into the UDPTransport in the Transport table.

In Code mode, the transport is initialized like this to open the transport in a master role

bool success = m_transport->Open(CDP::IO::Transport::OpenMode_Send);

... and it is closed like this:

try { m_transport->Close(); }
catch (std::exception const& e) { CDPMessage("%s::Close() : %s\n",e.what()); }
catch(...){ }

To write data to be sent on the transport:

unsigned int bytesSent = m_transport->Write(data,length);

To receive data from the transport:

double optionalTimeoutThatOverridesTransportConfiguration = 0.3; // seconds
unsigned int dataRead = m_transport->Read(receiveBuffer,maxSize,optionalTimeoutThatOverridesTransportConfiguration);

Overriding the Transport

In some cases it might be neccessary to add information to a Transport configuration that is used f.i. in a user-made IOServer. One way to do this is to make a new model xml file which has <BaseModel>Transport</BaseModel> and copy all the Attribute descriptions from the required model (TCPTransport or UDPTransport). In the IOServer library code, derive from the most related Transport class (TCP or UDP) and add code to expose the attribute(s). The IOServer itself must then make a new instance of this new transport instead of calling CDP::IO::Transport::Create(...).

Example ExtendedTCPTransport:

#include <IO/TCPTransport.h>

class ExtendedTCPTransport: public CDP::IO::TCPTransport
{
public:
  virtual void Configure(XMLElementEx* transportElement,CDPComponent* owner);
  virtual void FillNodeChildren(CDP::StudioAPI::NodeStream &serializer) const override;
};

void ExtendedTCPTransport::Configure(XMLElementEx *transportElement, CDPComponent *owner)
{
  TCPTransport::Configure(transportElement,owner);
  auto flags =  System::Base::PropertyCreateFlags()|System::Base::e_PropertyReadOnly | System::Base::e_PropertyReparent;
  System::Base::PropertyCreate(m_extraAttribute,owner,"ExtraAttribute",flags,transportElement);
}

void ExtendedTCPTransport::FillNodeChildren(CDP::StudioAPI::NodeStream &serializer) const
{
  TCPTransport::FillNodeChildren(serializer);
  serializer << CDP::StudioAPI::AbsorbedChild(m_extraAttribute);
}