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在使用非阻塞connect时#xff0c;发现在服务端没有运行时#xff0c;连接成功#xff0c;发现是对于connect返回为-1时#xff0c;对错误码没有做正确的处理#xff0c;只是对于errno为EINTR做了处理#xff0c;其它错误码时使用select判断是否可写#xff0c;可…问题
在使用非阻塞connect时发现在服务端没有运行时连接成功发现是对于connect返回为-1时对错误码没有做正确的处理只是对于errno为EINTR做了处理其它错误码时使用select判断是否可写可写就将套接字添加到reactor中这种处理方式是有问题的应该是在errno为EINPROGRESS时才使用select判断是否可写由于出错时套接字也会变为可写所以在判断为可写时需要调用getsockopt(s, SOL_SOCKET, SO_ERROR,…)判断没有出错才认为是连接成功的。
asio的异步连接处理
linux的处理
首先创建reactive_socket_connect_op操作调用start_connect_op在套接字为非阻塞或者将套接字设置为非阻塞调用connect发起连接如果错误码为in_progress或者would_block将reactive_socket_connect_op操作添加到事件循环中在套接字变为可写时会执行reactive_socket_connect_op_base基类的do_perform方法其会调用socket_ops#non_blocking_connect方法
template typename Handlervoid async_connect(implementation_type impl,const endpoint_type peer_endpoint, Handler handler){bool is_continuation boost_asio_handler_cont_helpers::is_continuation(handler);// Allocate and construct an operation to wrap the handler.typedef reactive_socket_connect_opHandler op;typename op::ptr p { boost::asio::detail::addressof(handler),boost_asio_handler_alloc_helpers::allocate(sizeof(op), handler), 0 };p.p new (p.v) op(impl.socket_, handler);BOOST_ASIO_HANDLER_CREATION((p.p, socket, impl, async_connect));start_connect_op(impl, p.p, is_continuation,peer_endpoint.data(), peer_endpoint.size());p.v p.p 0;}
};cpp
void reactive_socket_service_base::start_connect_op(reactive_socket_service_base::base_implementation_type impl,reactor_op* op, bool is_continuation,const socket_addr_type* addr, size_t addrlen)
{if ((impl.state_ socket_ops::non_blocking)|| socket_ops::set_internal_non_blocking(impl.socket_, impl.state_, true, op-ec_)){if (socket_ops::connect(impl.socket_, addr, addrlen, op-ec_) ! 0){if (op-ec_ boost::asio::error::in_progress|| op-ec_ boost::asio::error::would_block){op-ec_ boost::system::error_code();reactor_.start_op(reactor::connect_op, impl.socket_,impl.reactor_data_, op, is_continuation, false);return;}}}reactor_.post_immediate_completion(op, is_continuation);
}class reactive_socket_connect_op_base : public reactor_op
{
public:reactive_socket_connect_op_base(socket_type socket, func_type complete_func): reactor_op(reactive_socket_connect_op_base::do_perform, complete_func),socket_(socket){}static bool do_perform(reactor_op* base){reactive_socket_connect_op_base* o(static_castreactive_socket_connect_op_base*(base));return socket_ops::non_blocking_connect(o-socket_, o-ec_);}private:socket_type socket_;
};windows的处理
template typename Handlervoid async_connect(implementation_type impl,const endpoint_type peer_endpoint, Handler handler){// Allocate and construct an operation to wrap the handler.typedef win_iocp_socket_connect_opHandler op;typename op::ptr p { boost::asio::detail::addressof(handler),boost_asio_handler_alloc_helpers::allocate(sizeof(op), handler), 0 };p.p new (p.v) op(impl.socket_, handler);BOOST_ASIO_HANDLER_CREATION((p.p, socket, impl, async_connect));start_connect_op(impl, impl.protocol_.family(), impl.protocol_.type(),peer_endpoint.data(), static_castint(peer_endpoint.size()), p.p);p.v p.p 0;}
};void win_iocp_socket_service_base::start_connect_op(win_iocp_socket_service_base::base_implementation_type impl,int family, int type, const socket_addr_type* addr,std::size_t addrlen, win_iocp_socket_connect_op_base* op)
{// If ConnectEx is available, use that.if (family BOOST_ASIO_OS_DEF(AF_INET)|| family BOOST_ASIO_OS_DEF(AF_INET6)){if (connect_ex_fn connect_ex get_connect_ex(impl, type)){union address_union{socket_addr_type base;sockaddr_in4_type v4;sockaddr_in6_type v6;} a;using namespace std; // For memset.memset(a, 0, sizeof(a));a.base.sa_family family;socket_ops::bind(impl.socket_, a.base,family BOOST_ASIO_OS_DEF(AF_INET)? sizeof(a.v4) : sizeof(a.v6), op-ec_);if (op-ec_ op-ec_ ! boost::asio::error::invalid_argument){iocp_service_.post_immediate_completion(op, false);return;}op-connect_ex_ true;update_cancellation_thread_id(impl);iocp_service_.work_started();BOOL result connect_ex(impl.socket_,addr, static_castint(addrlen), 0, 0, 0, op);DWORD last_error ::WSAGetLastError();if (!result last_error ! WSA_IO_PENDING)iocp_service_.on_completion(op, last_error);elseiocp_service_.on_pending(op);return;}}// Otherwise, fall back to a reactor-based implementation.reactor r get_reactor();update_cancellation_thread_id(impl);if ((impl.state_ socket_ops::non_blocking) ! 0|| socket_ops::set_internal_non_blocking(impl.socket_, impl.state_, true, op-ec_)){if (socket_ops::connect(impl.socket_, addr, addrlen, op-ec_) ! 0){if (op-ec_ boost::asio::error::in_progress|| op-ec_ boost::asio::error::would_block){op-ec_ boost::system::error_code();r.start_op(reactor::connect_op, impl.socket_,impl.reactor_data_, op, false, false);return;}}}r.post_immediate_completion(op, false);
}class win_iocp_socket_connect_op_base : public reactor_op
{
public:win_iocp_socket_connect_op_base(socket_type socket, func_type complete_func): reactor_op(win_iocp_socket_connect_op_base::do_perform, complete_func),socket_(socket),connect_ex_(false){}static bool do_perform(reactor_op* base){win_iocp_socket_connect_op_base* o(static_castwin_iocp_socket_connect_op_base*(base));return socket_ops::non_blocking_connect(o-socket_, o-ec_);}socket_type socket_;bool connect_ex_;
};其中win_iocp_socket_connect_op_base 和reactive_socket_connect_op_base 都会调用non_blocking_connect其内部对window和linux作了区分处理window是调用select其设置的超时时间为0将套接字添加到可写以及异常集合中上。linux是调用poll添加POLLOUT事件超时时间设置为0。两个都是立即返回。如果返回的事件数为0说明还在尝试连接中。否则调用getsockopt判断是否出错没有出错说明连接成功了
bool non_blocking_connect(socket_type s, boost::system::error_code ec)
{// Check if the connect operation has finished. This is required since we may// get spurious readiness notifications from the reactor.
#if defined(BOOST_ASIO_WINDOWS) \|| defined(__CYGWIN__) \|| defined(__SYMBIAN32__)fd_set write_fds;FD_ZERO(write_fds);FD_SET(s, write_fds);fd_set except_fds;FD_ZERO(except_fds);FD_SET(s, except_fds);timeval zero_timeout;zero_timeout.tv_sec 0;zero_timeout.tv_usec 0;int ready ::select(s 1, 0, write_fds, except_fds, zero_timeout);
#else // defined(BOOST_ASIO_WINDOWS)// || defined(__CYGWIN__)// || defined(__SYMBIAN32__)pollfd fds;fds.fd s;fds.events POLLOUT;fds.revents 0;int ready ::poll(fds, 1, 0);
#endif // defined(BOOST_ASIO_WINDOWS)// || defined(__CYGWIN__)// || defined(__SYMBIAN32__)if (ready 0){// The asynchronous connect operation is still in progress.return false;}// Get the error code from the connect operation.int connect_error 0;size_t connect_error_len sizeof(connect_error);if (socket_ops::getsockopt(s, 0, SOL_SOCKET, SO_ERROR,connect_error, connect_error_len, ec) 0){if (connect_error){ec boost::system::error_code(connect_error,boost::asio::error::get_system_category());}elseec boost::system::error_code();}return true;
}qt的非阻塞连接处理
是通过QAbstractSocket::waitForConnected 首先开启QElapsedTimer定时器调用QAbstractSocketPrivate::_q_startConnecting发起连接内部调用QAbstractSocketPrivate::_q_connectToNextAddress调用QNativeSocketEngine::connectToHost,通过调用QNativeSocketEnginePrivate::nativeConnect即connect来发起连接 在连接没有成功时会设置套接字的可写socketEngine-setWriteNotificationEnabled(true);会为套接字添加写处理器QWriteNotifier当事件触发并且当前连接状态为ConnectingState时再次发起连接如果errno为EISCONN则更新状态为ConnectedState。同时会调用waitForWrite等待可写事件 对于windows系统如果返回的事件为不为0则表示连接成功否则调用getsockopt(d-socketDescriptor, SOL_SOCKET, SO_ERROR, (char *) value, valueSize)获取错误原因。 对于 linux系统当事件触发并且当前连接状态为ConnectingState时再次发起连接如果errno为EISCONN则更新状态为ConnectedState。waitForWrite时如果没有超时并且当前状态为ConnectingState则发起重连同时调用QAbstractSocketPrivate::_q_testConnection判断连接状态。
bool QNativeSocketEngine::waitForWrite(int msecs, bool *timedOut)
{Q_D(QNativeSocketEngine);Q_CHECK_VALID_SOCKETLAYER(QNativeSocketEngine::waitForWrite(), false);Q_CHECK_NOT_STATE(QNativeSocketEngine::waitForWrite(),QAbstractSocket::UnconnectedState, false);if (timedOut)*timedOut false;int ret d-nativeSelect(msecs, false);// On Windows, the socket is in connected state if a call to// select(writable) is successful. In this case we should not// issue a second call to WSAConnect()
#if defined (Q_OS_WIN)if (state() QAbstractSocket::ConnectingState) {if (ret 0) {setState(QAbstractSocket::ConnectedState);d_func()-fetchConnectionParameters();return true;} else {int value 0;int valueSize sizeof(value);if (::getsockopt(d-socketDescriptor, SOL_SOCKET, SO_ERROR, (char *) value, valueSize) 0) {if (value WSAECONNREFUSED) {d-setError(QAbstractSocket::ConnectionRefusedError, QNativeSocketEnginePrivate::ConnectionRefusedErrorString);d-socketState QAbstractSocket::UnconnectedState;return false;} else if (value WSAETIMEDOUT) {d-setError(QAbstractSocket::NetworkError, QNativeSocketEnginePrivate::ConnectionTimeOutErrorString);d-socketState QAbstractSocket::UnconnectedState;return false;} else if (value WSAEHOSTUNREACH) {d-setError(QAbstractSocket::NetworkError, QNativeSocketEnginePrivate::HostUnreachableErrorString);d-socketState QAbstractSocket::UnconnectedState;return false;}}}}
#endifif (ret 0) {if (timedOut)*timedOut true;d-setError(QAbstractSocket::SocketTimeoutError,QNativeSocketEnginePrivate::TimeOutErrorString);d-hasSetSocketError false; // A timeout error is temporary in waitFor functionsreturn false;} else if (state() QAbstractSocket::ConnectingState || (state() QAbstractSocket::BoundState d-socketDescriptor ! -1)) {connectToHost(d-peerAddress, d-peerPort);}return ret 0;
}
