Connectors

Table of Contents

• Creating a TCP Raw Socket Connector with the Json codec
• Creating a Unix Domain Socket Connector with the Msgpack codec
• Specifying Extra Socket Options
• Combining Connectors

wamp::Connector is the abstract base class for objects that can establish client transport endpoints.

The library currently supports two types of connectors:

Connector Factory	Declared in	For Transport
connector<TCodec>(AnyExecutor, TcpHost)	<cppwamp/tcp.hpp>	TCP raw socket
connector<TCodec>(AnyExecutor, UdsPath)	<cppwamp/uds.hpp>	Unix domain socket

When creating a connector, you must specify which codec class (aka serializer) to use for encoding WAMP messages. The following codecs are currently supported:

Codec	Declared in
wamp::Json	<cppwamp/json.hpp>
wamp::Msgpack	<cppwamp/msgpack.hpp>
wamp::Cbor	<cppwamp/cbor.hpp>

Connectors are created on the heap using the wamp::connector factory function as shown in the examples below. wamp::connector returns a std::shared_ptr to the newly created wamp::Connector.

After you have created one or more connectors, you pass them to the session API. The session object will then use these connectors while establishing a transport connection to the router.

Creating a TCP Raw Socket Connector with the Json codec

#include <cppwamp/json.hpp>
#include <cppwamp/session.hpp>
#include <cppwamp/tcp.hpp>
using namespace wamp;
 
AsioContext ioctx;   // AsioContext is an alias to boost::asio::io_context
auto tcp = connector<Json>(
    ioctx,           // The I/O context to use for asynchronous operations
    TcpHost(
        "127.0.0.1", // Host address
         8001        // Port number (could also be a service name string)
     )
);
 
// Create a `Session` object which shall later use the above connector
// when establishing a transport connection.
auto session = Session::create(tcp);

Creating a Unix Domain Socket Connector with the Msgpack codec

#include <cppwamp/session.hpp>
#include <cppwamp/msgpack.hpp>
#include <cppwamp/uds.hpp>
using namespace wamp;
 
AsioContext ioctx; // AsioContext is an alias to boost::asio::io_context
auto uds = connector<Msgpack>(
    ioctx,                 // I/O context to use for asynchronous operations
    UdsPath("path/to/uds") // Path name of the Unix domain socket
);
 
// Create a `Session` object which shall later use the above connector when
// establishing a transport connection.
auto session = Session::create(uds);

Specifying Extra Socket Options

The wamp::TcpHost object allows you to specify extra socket options. See the reference documentation for more details.

Likewise, the wamp::UdsPath object also allows you to specify extra socket options.

This snippet below shows how to create a TCP connector with a specified maximum incoming message length, as well as with Nagle's algorithm disabled:

using namespace wamp;
auto tcp = connector<Json>(
    ioctx,
    TcpHost("127.0.0.1", 8001)
        .withMaxRxLength(RawsockMaxLength::MB_1)
        .withOptions(TcpOptions.withNoDelay())
);

Combining Connectors

More than one Connector can be passed to a session object. In such cases, the session will successively attempt to establish a transport connection with each of the connectors until one succeeds. This allows you to specify "fallback" transports if the primary one fails to establish.

To achieve this, you must pass a std::vector of Connector shared pointers while creating session objects. The following example uses two TcpConnector objects, each specifying a different serializer:

#include <cppwamp/json.hpp>
#include <cppwamp/msgpack.hpp>
#include <cppwamp/session.hpp>
#include <cppwamp/tcp.hpp>
using namespace wamp;
 
AsioContext ioctx;
auto tcpJson = connector<Json>(ioctx, TcpHost("localhost", 8001));
auto tcpPack = connector<Msgpack>(ioctx, TcpHost("localhost", 8001));
 
// Create a `Session` object which shall later use both of the above
// connectors (in succession) when establishing a transport connection.
auto session = Session::create({tcpJson, tcpPack});

---

Next: Sessions