asio::async_connect

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

Functions
template<typename Protocol , typename SocketService , typename Iterator , typename ComposedConnectHandler >
	asio::ASIO_INITFN_RESULT_TYPE (ComposedConnectHandler, void(asio::error_code, Iterator)) async_connect(basic_socket< Protocol
SocketService Iterator	asio::ASIO_MOVE_ARG (ComposedConnectHandler) handler)
template<typename Protocol , typename SocketService , typename Iterator , typename ConnectCondition , typename ComposedConnectHandler >
	asio::ASIO_INITFN_RESULT_TYPE (ComposedConnectHandler, void(asio::error_code, Iterator)) async_connect(basic_socket< Protocol

Variables
SocketService &	asio::s
SocketService Iterator	asio::begin
SocketService Iterator Iterator	asio::end
SocketService Iterator ConnectCondition	asio::connect_condition

Detailed Description

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

Function Documentation

template<typename Protocol , typename SocketService , typename Iterator , typename ComposedConnectHandler >

asio::ASIO_INITFN_RESULT_TYPE ( ComposedConnectHandler  , void(asio::error_code, Iterator)    )

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.
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. Invocation of the handler will be performed in a manner equivalent to using asio::io_service::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.

Example

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

// ...

r.async_resolve(q, resolve_handler);

// ...

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

// ...

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

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.
end	An iterator pointing to the end 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. Invocation of the handler will be performed in a manner equivalent to using asio::io_service::post().

Example

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

// ...

r.async_resolve(q, resolve_handler);

// ...

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

// ...

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

template<typename Protocol , typename SocketService , typename Iterator , typename ConnectCondition , typename ComposedConnectHandler >

asio::ASIO_INITFN_RESULT_TYPE ( ComposedConnectHandler  , void(asio::error_code, Iterator)    )

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.
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: Iterator connect_condition( const asio::error_code& ec, Iterator 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 an iterator pointing to the next endpoint to be tried. The function object should return the next iterator, but is permitted to return a different iterator so that endpoints may be skipped. The implementation guarantees that the function object will never be called with the end iterator.
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. Invocation of the handler will be performed in a manner equivalent to using asio::io_service::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.

Example

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

 struct my_connect_condition
{
  template <typename Iterator>
  Iterator operator()(
      const asio::error_code& ec,
      Iterator next)
  {
    if (ec) std::cout << "Error: " << ec.message() << std::endl;
    std::cout << "Trying: " << next->endpoint() << std::endl;
    return next;
  }
}; 

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

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

// ...

r.async_resolve(q, resolve_handler);

// ...

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

// ...

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

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.
end	An iterator pointing to the end 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: Iterator connect_condition( const asio::error_code& ec, Iterator 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 an iterator pointing to the next endpoint to be tried. The function object should return the next iterator, but is permitted to return a different iterator so that endpoints may be skipped. The implementation guarantees that the function object will never be called with the end iterator.
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. Invocation of the handler will be performed in a manner equivalent to using asio::io_service::post().

Example

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

 struct my_connect_condition
{
  template <typename Iterator>
  Iterator operator()(
      const asio::error_code& ec,
      Iterator next)
  {
    if (ec) std::cout << "Error: " << ec.message() << std::endl;
    std::cout << "Trying: " << next->endpoint() << std::endl;
    return next;
  }
}; 

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

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

// ...

r.async_resolve(q, resolve_handler);

// ...

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

// ...

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

SocketService Iterator asio::ASIO_MOVE_ARG

(

ComposedConnectHandler

)

Definition at line 326 of file connect.hpp.

Variable Documentation

SocketService Iterator asio::begin

Definition at line 521 of file connect.hpp.

SocketService Iterator Iterator ConnectCondition asio::connect_condition

Definition at line 702 of file connect.hpp.

SocketService Iterator Iterator asio::end

Definition at line 592 of file connect.hpp.

SocketService & asio::s

Definition at line 521 of file connect.hpp.