window API一天一练之邮槽

邮槽通信的进程分为服务端和客户端.服务端创建邮槽,客户端通过邮槽名打开邮槽,获得句柄后可以向邮槽写数据. 邮槽通信是单向通信,只能由客户端向服务端发送数据.下面来看看有关邮槽的几个API

HANDLE WINAPICreateMailslot(

_In_      LPCTSTR lpName,

_In_      DWORDnMaxMessageSize,

_In_      DWORDlReadTimeout,

_In_opt_  LPSECURITY_ATTRIBUTESlpSecurityAttributes

);

功能:创建一个邮槽

参数:  lpName   指定的邮槽名,格式必须为  \\.\mailslot\[path]name

nMaxMessageSize  可以写到邮槽中的单个消息的最大字节数,如果为0则表示可以是任意大小的消息.

lReadTimeout    读取操作可以等待多久,0表示没有可读的消息则直接返回, MAILSLOT_WAIT_FOREVER表示一直等待可读消息.

lpSecurityAttributes  安全属性结构体指针,   可以为NULL

返回值: 如果成功,返回邮槽句柄,服务端通过句柄操作邮槽.如果失败则返回INVALID_HANDLE_VALUE

BOOL WINAPI GetMailslotInfo(

  _In_       HANDLE hMailslot,

  _Out_opt_  LPDWORD lpMaxMessageSize,

  _Out_opt_  LPDWORD lpNextSize,

  _Out_opt_  LPDWORD lpMessageCount,

  _Out_opt_  LPDWORD lpReadTimeout

);

功能:获取有关邮槽的信息

参数: hMailslot  邮槽句柄

lpMaxMessageSize     单个消息的最大字节数, 也可以为NULL

lpNextSize   下一个消息的大小,可以为NULL,为MAILSLOT_NO_MESSAGE表示没有下一个消息

lpMessageCount  等待读取的消息数, 可以为NULL,

lpReadTimeout   等待可读消息的时间, 也可以为NULL

返回值:成功返回非0,失败返回0

BOOL WINAPI SetMailslotInfo(

  _In_  HANDLE hMailslot,

  _In_  DWORD lReadTimeout

);

功能:设置等待可读消息的超时时间

服务端通过ReadFile从邮槽中读取数据，客户端通过CreateFile打开邮槽，WriteFile向邮槽写数据。以下是我用Qt做的简单验证程序，由于不熟悉window窗台程序，所以只能用Qt了。

客户端代码

MailSlotClient::MailSlotClient(QWidget *parent, Qt::WFlags flags)
	: QDialog(parent, flags)
{
	m_pMailSlotNameLbl = new QLabel(tr("MailSlot Name:"),this);
	m_pMailSlotNameLEdit = new QLineEdit(this);
	m_pMessageText = new QTextEdit(this);
	m_pMainLayout = new QGridLayout(this);
	m_pSendMessageBtn = new QPushButton(tr("Send Message "),this);
	this->setLayout(m_pMainLayout);
	m_pMainLayout->addWidget(m_pMailSlotNameLbl,0,0,1,1);
	m_pMainLayout->addWidget(m_pMailSlotNameLEdit,0,1,1,1);
	m_pMainLayout->addWidget(m_pSendMessageBtn,0,2,1,1);
	m_pMainLayout->addWidget(m_pMessageText,1,0,4,4);
	connect(m_pSendMessageBtn,SIGNAL(clicked()),this,SLOT(SendMessageSlot()));
	//ui.setupUi(this);
}

MailSlotClient::~MailSlotClient()
{

}

void MailSlotClient::SendMessageSlot()
{
	QString name = m_pMailSlotNameLEdit->text();
	string szMailSlotName = (string("\\\\.\\mailslot\\") + name.toStdString()).c_str();
	//LPSTR szMailSlotName = "\\\\.\\mailslot\\simplemailslot";
	HANDLE hFile ;
	hFile = CreateFile(szMailSlotName.c_str(),GENERIC_WRITE,FILE_SHARE_READ,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
	if (hFile == INVALID_HANDLE_VALUE)
	{
		QMessageBox::information(this,tr("提示"),tr("打开邮槽失败！"),QMessageBox::Ok);
		return ;
	}
	DWORD dwWriteSize;
	string message = m_pMessageText->toPlainText().toStdString();
	WriteFile(hFile,message.c_str(),message.size(),&dwWriteSize,NULL);
	CloseHandle(hFile);
}

服务端代码：

MailSlotServer::MailSlotServer(QWidget *parent, Qt::WFlags flags)
	: QDialog(parent, flags)
{
	m_pMailSlotNameLbl = new QLabel(tr("MailSlot Name:"),this);
	m_pMailSlotNameLEdit = new QLineEdit(this);
	m_pMessageText = new QTextEdit(this);
	m_pMainLayout = new QGridLayout(this);
	m_pCreateMailSlotBtn = new QPushButton(tr("Create MailSlot "),this);
	this->setLayout(m_pMainLayout);
	m_pMainLayout->addWidget(m_pMailSlotNameLbl,0,0,1,1);
	m_pMainLayout->addWidget(m_pMailSlotNameLEdit,0,1,1,1);
	m_pMainLayout->addWidget(m_pCreateMailSlotBtn,0,2,1,1);
	m_pMainLayout->addWidget(m_pMessageText,1,0,4,4);
	connect(m_pCreateMailSlotBtn,SIGNAL(clicked()),this,SLOT(CreateMailSlot()));
}

MailSlotServer::~MailSlotServer()
{

}

void MailSlotServer::CreateMailSlot()
{
	HANDLE hMailSlot;
	QString name = m_pMailSlotNameLEdit->text();
	string szMailSlotName = (string("\\\\.\\mailslot\\") + name.toStdString()).c_str();
	hMailSlot = CreateMailslot(szMailSlotName.c_str() ,0,MAILSLOT_WAIT_FOREVER,NULL);

	if (hMailSlot == INVALID_HANDLE_VALUE)
	{
		QMessageBox::information(this,tr("提示"),tr("创建邮槽失败！"),QMessageBox::Ok);
		return ;
	}

	DWORD dwMessageCount = 0;
	DWORD dwMessageSize = 0;
	DWORD dwReadSize = 0;
	bool bFinish =false;
	while (TRUE)
	{
		BOOL bResult = GetMailslotInfo(hMailSlot,NULL,&dwMessageSize,&dwMessageCount,NULL);
		if (!bResult)
		{
			QMessageBox::information(this,tr("提示"),tr("获取邮槽信息失败！"),QMessageBox::Ok);
			return ;
		}
			while (dwMessageCount != 0)
			{
				char *lpBuffer = new char[dwMessageSize];
				memset(lpBuffer,0,dwMessageSize);
				ReadFile(hMailSlot,lpBuffer,dwMessageSize,&dwReadSize,NULL);

				m_pMessageText->setText(QString::fromStdString(lpBuffer));
				GetMailslotInfo(hMailSlot,NULL,&dwMessageSize,&dwMessageCount,NULL);
				bFinish = true;
			}
		if (bFinish)   //读取完了就返回，不然一直卡住就没法显示接收到的数据了

		{
			return;
		}
	}
}

先启动服务端，输入邮槽名，创建邮槽，程序循环等待客户端发来数据。接收到数据后显示。再启动客户端，输入邮槽名，输入要发送的数据，点击发送，数据将显示在服务端。