asio::async_connect

The async_connect function is a composed asynchronous operation that establishes a socket connection by trying each endpoint in a sequence. More...

Functions
template<typename Protocol , typename Executor , typename EndpointSequence , ASIO_COMPLETION_TOKEN_FOR(void(asio::error_code, typename Protocol::endpoint)) RangeConnectHandler ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor) >
	asio::ASIO_INITFN_AUTO_RESULT_TYPE (RangeConnectHandler, void(asio::error_code, typename Protocol::endpoint)) async_connect(basic_socket< Protocol
	Asynchronously establishes a socket connection by trying each endpoint in a sequence. More...
Executor const EndpointSequence	asio::ASIO_MOVE_ARG (RangeConnectHandler) handler ASIO_DEFAULT_COMPLETION_TOKEN(Executor)
template<typename Protocol , typename Executor , typename Iterator , ASIO_COMPLETION_TOKEN_FOR(void(asio::error_code, Iterator)) IteratorConnectHandler ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor) >
Executor const EndpointSequence enable_if< is_endpoint_sequence< EndpointSequence >::value >::type *	asio::ASIO_INITFN_AUTO_RESULT_TYPE (IteratorConnectHandler, void(asio::error_code, Iterator)) async_connect(basic_socket< Protocol
	(Deprecated: Use range overload.) Asynchronously establishes a socket connection by trying each endpoint in a sequence. More...
Executor const EndpointSequence enable_if< is_endpoint_sequence< EndpointSequence >::value >::type Executor Iterator	asio::ASIO_MOVE_ARG (IteratorConnectHandler) handler ASIO_DEFAULT_COMPLETION_TOKEN(Executor)
template<typename Protocol , typename Executor , typename EndpointSequence , typename ConnectCondition , ASIO_COMPLETION_TOKEN_FOR(void(asio::error_code, typename Protocol::endpoint)) RangeConnectHandler ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor) >
	asio::ASIO_INITFN_AUTO_RESULT_TYPE (RangeConnectHandler, void(asio::error_code, typename Protocol::endpoint)) async_connect(basic_socket< Protocol
	Asynchronously establishes a socket connection by trying each endpoint in a sequence. More...
template<typename Protocol , typename Executor , typename Iterator , typename ConnectCondition , ASIO_COMPLETION_TOKEN_FOR(void(asio::error_code, Iterator)) IteratorConnectHandler ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor) >
Executor const EndpointSequence ConnectCondition enable_if< is_endpoint_sequence< EndpointSequence >::value >::type *	asio::ASIO_INITFN_AUTO_RESULT_TYPE (IteratorConnectHandler, void(asio::error_code, Iterator)) async_connect(basic_socket< Protocol
	(Deprecated: Use range overload.) Asynchronously establishes a socket connection by trying each endpoint in a sequence. More...

Variables
Executor &	asio::s
Executor const EndpointSequence &	asio::endpoints
Executor const EndpointSequence enable_if< is_endpoint_sequence< EndpointSequence >::value >::type Executor Iterator	asio::begin
Executor const EndpointSequence enable_if< is_endpoint_sequence< EndpointSequence >::value >::type Executor Iterator enable_if<!is_endpoint_sequence< Iterator >::value >::type Executor Iterator Iterator	asio::end
Executor const EndpointSequence ConnectCondition	asio::connect_condition

Detailed Description

The async_connect function is a composed asynchronous operation that establishes a socket connection by trying each endpoint in a sequence.

Function Documentation

ASIO_INITFN_AUTO_RESULT_TYPE() [1/4]

template<typename Protocol , typename Executor , typename EndpointSequence , ASIO_COMPLETION_TOKEN_FOR(void(asio::error_code, typename Protocol::endpoint)) RangeConnectHandler ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor) >

asio::ASIO_INITFN_AUTO_RESULT_TYPE ( RangeConnectHandler  , void(asio::error_code, typename Protocol::endpoint)    )

inline

Asynchronously establishes a socket connection by trying each endpoint in a sequence.

This function attempts to connect a socket to one of a sequence of endpoints. It does this by repeated calls to the socket's async_connect member function, once for each endpoint in the sequence, until a connection is successfully established.

Parameters

s	The socket to be connected. If the socket is already open, it will be closed.
endpoints	A sequence of endpoints.
handler	The handler to be called when the connect operation completes. Copies will be made of the handler as required. The function signature of the handler must be: void handler( // Result of operation. if the sequence is empty, set to // asio::error::not_found. Otherwise, contains the // error from the last connection attempt. const asio::error_code& error, // On success, the successfully connected endpoint. // Otherwise, a default-constructed endpoint. const typename Protocol::endpoint& endpoint ); Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. On immediate completion, invocation of the handler will be performed in a manner equivalent to using asio::post().

Example

 tcp::resolver r(my_context);
tcp::resolver::query q("host", "service");
tcp::socket s(my_context);

// ...

r.async_resolve(q, resolve_handler);

// ...

void resolve_handler(
    const asio::error_code& ec,
    tcp::resolver::results_type results)
{
  if (!ec)
  {
    asio::async_connect(s, results, connect_handler);
  }
}

// ...

void connect_handler(
    const asio::error_code& ec,
    const tcp::endpoint& endpoint)
{
  // ...
} 

ASIO_INITFN_AUTO_RESULT_TYPE() [2/4]

template<typename Protocol , typename Executor , typename Iterator , ASIO_COMPLETION_TOKEN_FOR(void(asio::error_code, Iterator)) IteratorConnectHandler ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor) >

Executor const EndpointSequence enable_if< is_endpoint_sequence< EndpointSequence >::value >::type * asio::ASIO_INITFN_AUTO_RESULT_TYPE ( IteratorConnectHandler  , void(asio::error_code, Iterator)    )

inline

Initial value:

{
  return async_initiate<RangeConnectHandler,
    void (asio::error_code, typename Protocol::endpoint)>(
      detail::initiate_async_range_connect<Protocol, Executor>(s),
      handler, endpoints, detail::default_connect_condition())

(Deprecated: Use range overload.) Asynchronously establishes a socket connection by trying each endpoint in a sequence.

This function attempts to connect a socket to one of a sequence of endpoints. It does this by repeated calls to the socket's async_connect member function, once for each endpoint in the sequence, until a connection is successfully established.

Parameters

s	The socket to be connected. If the socket is already open, it will be closed.
begin	An iterator pointing to the start of a sequence of endpoints.
handler	The handler to be called when the connect operation completes. Copies will be made of the handler as required. The function signature of the handler must be: void handler( // Result of operation. if the sequence is empty, set to // asio::error::not_found. Otherwise, contains the // error from the last connection attempt. const asio::error_code& error, // On success, an iterator denoting the successfully // connected endpoint. Otherwise, the end iterator. Iterator iterator ); Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. On immediate completion, invocation of the handler will be performed in a manner equivalent to using asio::post().

Note

This overload assumes that a default constructed object of type Iterator represents the end of the sequence. This is a valid assumption for iterator types such as asio::ip::tcp::resolver::iterator.

ASIO_INITFN_AUTO_RESULT_TYPE() [3/4]

template<typename Protocol , typename Executor , typename EndpointSequence , typename ConnectCondition , ASIO_COMPLETION_TOKEN_FOR(void(asio::error_code, typename Protocol::endpoint)) RangeConnectHandler ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor) >

asio::ASIO_INITFN_AUTO_RESULT_TYPE ( RangeConnectHandler  , void(asio::error_code, typename Protocol::endpoint)    )

inline

Asynchronously establishes a socket connection by trying each endpoint in a sequence.

This function attempts to connect a socket to one of a sequence of endpoints. It does this by repeated calls to the socket's async_connect member function, once for each endpoint in the sequence, until a connection is successfully established.

Parameters

s	The socket to be connected. If the socket is already open, it will be closed.
endpoints	A sequence of endpoints.
connect_condition	A function object that is called prior to each connection attempt. The signature of the function object must be: bool connect_condition( const asio::error_code& ec, const typename Protocol::endpoint& next); The ec parameter contains the result from the most recent connect operation. Before the first connection attempt, ec is always set to indicate success. The next parameter is the next endpoint to be tried. The function object should return true if the next endpoint should be tried, and false if it should be skipped.
handler	The handler to be called when the connect operation completes. Copies will be made of the handler as required. The function signature of the handler must be: void handler( // Result of operation. if the sequence is empty, set to // asio::error::not_found. Otherwise, contains the // error from the last connection attempt. const asio::error_code& error, // On success, an iterator denoting the successfully // connected endpoint. Otherwise, the end iterator. Iterator iterator ); Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. On immediate completion, invocation of the handler will be performed in a manner equivalent to using asio::post().

Example

The following connect condition function object can be used to output information about the individual connection attempts:

 struct my_connect_condition
{
  bool operator()(
      const asio::error_code& ec,
      const::tcp::endpoint& next)
  {
    if (ec) std::cout << "Error: " << ec.message() << std::endl;
    std::cout << "Trying: " << next << std::endl;
    return true;
  }
}; 

It would be used with the asio::connect function as follows:

 tcp::resolver r(my_context);
tcp::resolver::query q("host", "service");
tcp::socket s(my_context);

// ...

r.async_resolve(q, resolve_handler);

// ...

void resolve_handler(
    const asio::error_code& ec,
    tcp::resolver::results_type results)
{
  if (!ec)
  {
    asio::async_connect(s, results,
        my_connect_condition(),
        connect_handler);
  }
}

// ...

void connect_handler(
    const asio::error_code& ec,
    const tcp::endpoint& endpoint)
{
  if (ec)
  {
    // An error occurred.
  }
  else
  {
    std::cout << "Connected to: " << endpoint << std::endl;
  }
} 

ASIO_INITFN_AUTO_RESULT_TYPE() [4/4]

template<typename Protocol , typename Executor , typename Iterator , typename ConnectCondition , ASIO_COMPLETION_TOKEN_FOR(void(asio::error_code, Iterator)) IteratorConnectHandler ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor) >

Executor const EndpointSequence ConnectCondition enable_if< is_endpoint_sequence< EndpointSequence >::value >::type * asio::ASIO_INITFN_AUTO_RESULT_TYPE ( IteratorConnectHandler  , void(asio::error_code, Iterator)    )

inline

Initial value:

{
  return async_initiate<RangeConnectHandler,
    void (asio::error_code, typename Protocol::endpoint)>(
      detail::initiate_async_range_connect<Protocol, Executor>(s),
      handler, endpoints, connect_condition)

(Deprecated: Use range overload.) Asynchronously establishes a socket connection by trying each endpoint in a sequence.

This function attempts to connect a socket to one of a sequence of endpoints. It does this by repeated calls to the socket's async_connect member function, once for each endpoint in the sequence, until a connection is successfully established.

Parameters

s	The socket to be connected. If the socket is already open, it will be closed.
begin	An iterator pointing to the start of a sequence of endpoints.
connect_condition	A function object that is called prior to each connection attempt. The signature of the function object must be: bool connect_condition( const asio::error_code& ec, const typename Protocol::endpoint& next); The ec parameter contains the result from the most recent connect operation. Before the first connection attempt, ec is always set to indicate success. The next parameter is the next endpoint to be tried. The function object should return true if the next endpoint should be tried, and false if it should be skipped.
handler	The handler to be called when the connect operation completes. Copies will be made of the handler as required. The function signature of the handler must be: void handler( // Result of operation. if the sequence is empty, set to // asio::error::not_found. Otherwise, contains the // error from the last connection attempt. const asio::error_code& error, // On success, an iterator denoting the successfully // connected endpoint. Otherwise, the end iterator. Iterator iterator ); Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. On immediate completion, invocation of the handler will be performed in a manner equivalent to using asio::post().

Note

This overload assumes that a default constructed object of type Iterator represents the end of the sequence. This is a valid assumption for iterator types such as asio::ip::tcp::resolver::iterator.