问题
I am using boost::asio::connect on a tcp::socket. When all goes fine, the connect returns immediately but on a poor network, the connect times out after a log wait of 15 seconds. I cannot afford to wait that long and so want to reduce the timeout. Unfortunately I have not come across any solution so far.
I see solutions where async_wait is been used together with deadline_timer but all those examples are for receive / send operations and not for connect.
Can anyone help me with a sample code for boost::asio::connect(socket, endpoints);. Requirement is that it should timeout in 5 seconds instead of 15.
回答1:
Have you take a look to the following example? it contains a sample code an async_connect with timeout.
http://www.boost.org/doc/libs/1_52_0/doc/html/boost_asio/example/timeouts/blocking_tcp_client.cpp
The connect with timeout method could be implemented using the following code:
void connect(const std::string& host, const std::string& service,
boost::posix_time::time_duration timeout) {
// Resolve the host name and service to a list of endpoints.
tcp::resolver::query query(host, service);
tcp::resolver::iterator iter = tcp::resolver(io_service_).resolve(query);
// Set a deadline for the asynchronous operation. As a host name may
// resolve to multiple endpoints, this function uses the composed operation
// async_connect. The deadline applies to the entire operation, rather than
// individual connection attempts.
deadline_.expires_from_now(timeout);
// Set up the variable that receives the result of the asynchronous
// operation. The error code is set to would_block to signal that the
// operation is incomplete. Asio guarantees that its asynchronous
// operations will never fail with would_block, so any other value in
// ec indicates completion.
boost::system::error_code ec = boost::asio::error::would_block;
// Start the asynchronous operation itself. The boost::lambda function
// object is used as a callback and will update the ec variable when the
// operation completes. The blocking_udp_client.cpp example shows how you
// can use boost::bind rather than boost::lambda.
boost::asio::async_connect(socket_, iter, var(ec) = _1);
// Block until the asynchronous operation has completed.
do io_service_.run_one(); while (ec == boost::asio::error::would_block);
// Determine whether a connection was successfully established. The
// deadline actor may have had a chance to run and close our socket, even
// though the connect operation notionally succeeded. Therefore we must
// check whether the socket is still open before deciding if we succeeded
// or failed.
if (ec || !socket_.is_open())
throw boost::system::system_error(
ec ? ec : boost::asio::error::operation_aborted);
}
来源：https://stackoverflow.com/questions/32692195/set-timeout-for-boost-socket-connect