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</center></div><font FACE="Times New Roman" SIZE="3"><b><p ALIGN="CENTER"></b></font><font color="#3973DE" FACE="Times New Roman" SIZE="3">12. 4 </font><font SIZE="3" color="#3973DE">一个通信演示程序</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3"> </font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3">为了使读者更好地掌握本章的概念，这里举一个具体实例来说明问题。如图</font><font FACE="Times New Roman" SIZE="3">12.1</font><font SIZE="3">所示，例子程序名为</font><font FACE="Times New Roman" SIZE="3">Terminal</font><font SIZE="3">，是一个简单的</font><font FACE="Times New Roman" SIZE="3">TTY</font><font SIZE="3">终端仿真程序。读者可以用该程序打开一个串行口，该程序会把用户的键盘输入发送给串行口，并把从串口接收到的字符显示在视图中。用户通过选择</font><font FACE="Times New Roman" SIZE="3">File->Connect</font><font SIZE="3">命令来打开串行口，选择</font><font FACE="Times New Roman" SIZE="3">File->Disconnect</font><font SIZE="3">命令则关闭串行口。</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="center"></font><font SIZE="3"><img src="T12_1.gif" alt="T12_1.tif (174388 bytes)" WIDTH="452" HEIGHT="322"></font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="center"></font><font SIZE="3">图</font><font FACE="Times New Roman" SIZE="3">12.1
Terminal</font><font SIZE="3">终端仿真程序</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3"> </font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3">当用户选择</font><font FACE="Times New Roman" SIZE="3">File->Settings...</font><font SIZE="3">命令时，会弹出一个</font><font FACE="Times New Roman" SIZE="3">Communication settings</font><font SIZE="3">对话框，如图</font><font FACE="Times New Roman" SIZE="3">12.2</font><font SIZE="3">所示。该对话框主要用来设置串行口，包括端口、波特率、每字节位数、校验、停止位数和流控制。</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="center"></font><font SIZE="3"><img src="T12_2.gif" alt="T12_2.tif (92960 bytes)" WIDTH="339" HEIGHT="244"></font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="center"></font><font SIZE="3">图</font><font FACE="Times New Roman" SIZE="3">12.2
Communication settings</font><font SIZE="3">对话框</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3"> </font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3">通过该对话框也可以设置</font><font FACE="Times New Roman" SIZE="3">TTY</font><font SIZE="3">终端仿真的属性，如果选择</font><font FACE="Times New Roman" SIZE="3">New Line</font><font SIZE="3">（自动换行），那么每当从串口读到回车符</font><font FACE="Times New Roman" SIZE="3">(</font><font SIZE="3">‘</font><font FACE="Times New Roman" SIZE="3">\r</font><font SIZE="3">’</font><font FACE="Times New Roman" SIZE="3">)</font><font SIZE="3">时，视图中的正文就会换行，否则，只有在读到换行符</font><font FACE="Times New Roman" SIZE="3">(</font><font SIZE="3">‘</font><font FACE="Times New Roman" SIZE="3">\n</font><font SIZE="3">’</font><font FACE="Times New Roman" SIZE="3">)</font><font SIZE="3">时才会换行。如果选择</font><font FACE="Times New Roman" SIZE="3">Local echo</font><font SIZE="3">（本地回显），那么发送的字符会在视图中显示出来。</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3">终端仿真程序的特点是数据的传输没有规律。因为键盘输入速度有限，所以发送的数据量较小，但接收的数据源是不确定的，所以有可能会有大量数据高速涌入的情况发生。根据</font><font FACE="Times New Roman" SIZE="3">Terminal</font><font SIZE="3">的这些特性，我们在程序中创建了一个辅助工作者线程专门来监视串行口的输入。由于写入串行口的数据量不大，不会太费时，所以在主线程中完成写端口的任务是可以的，不必另外创建线程。</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3">现在就让我们开始工作。请读者按下面几步进行：</p>
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<p ALIGN="JUSTIFY">用</font><font FACE="Times New Roman" SIZE="3">AppWizard</font><font SIZE="3">建立一个名为</font><font FACE="Times New Roman" SIZE="3">Terminal</font><font SIZE="3">的</font><font FACE="Times New Roman" SIZE="3">MFC</font><font SIZE="3">应用程序。在</font><font FACE="Times New Roman" SIZE="3">MFC AppWizard</font><font SIZE="3">对话框的第</font><font FACE="Times New Roman" SIZE="3">1</font><font SIZE="3">步选择</font><font FACE="Times New Roman" SIZE="3">Single document</font><font SIZE="3">，在第</font><font FACE="Times New Roman" SIZE="3">4</font><font SIZE="3">步去掉</font><font FACE="Times New Roman" SIZE="3">Docking toolbar</font><font SIZE="3">的选择，在第</font><font FACE="Times New Roman" SIZE="3">6</font><font SIZE="3">步把</font><font FACE="Times New Roman" SIZE="3">CTerminalView</font><font SIZE="3">的基类改为</font><font FACE="Times New Roman" SIZE="3">CEditView</font><font SIZE="3">。</p>
<p ALIGN="JUSTIFY">在</font><font FACE="Times New Roman" SIZE="3">Terminal</font><font SIZE="3">工程的资源视图中打开</font><font FACE="Times New Roman" SIZE="3">IDR_MAINFRAME</font><font SIZE="3">菜单资源。去掉</font><font FACE="Times New Roman" SIZE="3">Edit</font><font SIZE="3">菜单和</font><font FACE="Times New Roman" SIZE="3">View</font><font SIZE="3">菜单，并去掉</font><font FACE="Times New Roman" SIZE="3">File</font><font SIZE="3">菜单中除</font><font FACE="Times New Roman" SIZE="3">Exit</font><font SIZE="3">以外的所有菜单项。然后在</font><font FACE="Times New Roman" SIZE="3">File</font><font SIZE="3">菜单中加入三个菜单项，如表</font><font FACE="Times New Roman" SIZE="3">12.5</font><font SIZE="3">所示。</p>
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<p><b><font SIZE="3"> </p>
<p ALIGN="CENTER">表</font><font FACE="Times New Roman" SIZE="3">12.5 </font><font SIZE="3">新菜单项</font></b></p>
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<td WIDTH="50%"><font SIZE="3"><b><p ALIGN="JUSTIFY">标题</b></font></td>
<td WIDTH="50%"><font FACE="Times New Roman" SIZE="3"><b><p ALIGN="JUSTIFY">ID</b></font></td>
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<td WIDTH="50%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Settings...</font></td>
<td WIDTH="50%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">ID_FILE_SETTINGS</font></td>
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<td WIDTH="50%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Connect</font></td>
<td WIDTH="50%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">ID_FILE_CONNECT</font></td>
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<td WIDTH="50%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Disconnect</font></td>
<td WIDTH="50%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">ID_FILE_DISCONNECT</font></td>
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<p><font SIZE="3"> </font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3"> </font><font FACE="Times New Roman" SIZE="3"></p>
<blockquote>
<blockquote>
</font><font SIZE="3"><p ALIGN="JUSTIFY">用</font><font FACE="Times New Roman" SIZE="3">ClassWizard</font><font SIZE="3">为</font><font FACE="Times New Roman" SIZE="3">CTerminalDoc</font><font SIZE="3">类创建三个与上表菜单消息对应的命令处理函数，使用缺省的函数名。为</font><font FACE="Times New Roman" SIZE="3">ID_FILE_CONNECT</font><font SIZE="3">和</font><font FACE="Times New Roman" SIZE="3">ID_FILE_DISCONNECT</font><font SIZE="3">命令创建命令更新处理函数。另外，用</font><font FACE="Times New Roman" SIZE="3">ClassWizard</font><font SIZE="3">为该类加入</font><font FACE="Times New Roman" SIZE="3">CanCloseFrame</font><font SIZE="3">成员函数。</p>
<p ALIGN="JUSTIFY">用</font><font FACE="Times New Roman" SIZE="3">ClassWizard</font><font SIZE="3">为</font><font FACE="Times New Roman" SIZE="3">CTerminalView</font><font SIZE="3">类创建</font><font FACE="Times New Roman" SIZE="3">OnChar</font><font SIZE="3">函数，该函数用来把用户键入的字符向串行口输出。</p>
<p ALIGN="JUSTIFY">新建一个对话框模板资源，令其</font><font FACE="Times New Roman" SIZE="3">ID</font><font SIZE="3">为</font><font FACE="Times New Roman" SIZE="3">IDD_COMSETTINGS</font><font SIZE="3">。请按图</font><font FACE="Times New Roman" SIZE="3">12.2</font><font SIZE="3">和表</font><font FACE="Times New Roman" SIZE="3">12.6</font><font SIZE="3">设计对话框模板。</p>
</font>
</blockquote>
</blockquote>
<p><b><font SIZE="3"> </p>
<p ALIGN="CENTER">表</font><font FACE="Times New Roman" SIZE="3">12.6 </font><font SIZE="3">通信设置对话框中的主要控件</font></b></p>
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<td WIDTH="29%"><font SIZE="3"><b><p ALIGN="JUSTIFY">控件</b></font></td>
<td WIDTH="26%"><font FACE="Times New Roman" SIZE="3"><b><p ALIGN="JUSTIFY">ID</b></font></td>
<td WIDTH="44%"><font SIZE="3"><b><p ALIGN="JUSTIFY">属性设置</b></font></td>
</tr>
<tr>
<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Base options</font><font SIZE="3">组框</font></td>
<td WIDTH="26%"><font SIZE="3"><p ALIGN="JUSTIFY">缺省</font></td>
<td WIDTH="44%"><font SIZE="3"><p ALIGN="JUSTIFY">标题为</font><font FACE="Times New Roman" SIZE="3">Base options</font></td>
</tr>
<tr>
<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Port</font><font SIZE="3">组合框</font></td>
<td WIDTH="26%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">IDC_PORT</font></td>
<td WIDTH="44%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Drop List</font><font SIZE="3">，不选</font><font FACE="Times New Roman" SIZE="3">Sort</font><font SIZE="3">，初始列表为</font><font FACE="Times New Roman" SIZE="3">COM1</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">COM2</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">COM3</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">COM4</font></td>
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<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Baud rate</font><font SIZE="3">组合框</font></td>
<td WIDTH="26%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">IDC_BAUD</font></td>
<td WIDTH="44%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Drop List</font><font SIZE="3">，不选</font><font FACE="Times New Roman" SIZE="3">Sort</font><font SIZE="3">，初始列表为</font><font FACE="Times New Roman" SIZE="3">300</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">600</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">1200</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">2400</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">9600</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">14400</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">19200</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">38400</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">57600</font></td>
</tr>
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<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Data bits</font><font SIZE="3">组合框</font></td>
<td WIDTH="26%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">IDC_DATABITS</font></td>
<td WIDTH="44%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Drop List</font><font SIZE="3">，不选</font><font FACE="Times New Roman" SIZE="3">Sort</font><font SIZE="3">，初列表为</font><font FACE="Times New Roman" SIZE="3">5</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">6</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">7</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">8</font></td>
</tr>
<tr>
<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Parity</font><font SIZE="3">组合框</font></td>
<td WIDTH="26%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">IDC_PARITY</font></td>
<td WIDTH="44%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Drop List</font><font SIZE="3">，不选</font><font FACE="Times New Roman" SIZE="3">Sort</font><font SIZE="3">，初列表为</font><font FACE="Times New Roman" SIZE="3">None</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">Even</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">Odd</font></td>
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<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Stop bits</font><font SIZE="3">组合框</font></td>
<td WIDTH="26%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">IDC_STOPBITS</font></td>
<td WIDTH="44%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Drop List</font><font SIZE="3">，不选</font><font FACE="Times New Roman" SIZE="3">Sort</font><font SIZE="3">，初列表为</font><font FACE="Times New Roman" SIZE="3">1</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">1.5</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">2</font></td>
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<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">Flow control</font><font SIZE="3">组框</font></td>
<td WIDTH="26%"><font SIZE="3"><p ALIGN="JUSTIFY">缺省</font></td>
<td WIDTH="44%"><font SIZE="3"><p ALIGN="JUSTIFY">标题为</font><font FACE="Times New Roman" SIZE="3">Flow control</font></td>
</tr>
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<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">None</font><font SIZE="3">单选按钮</font></td>
<td WIDTH="26%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">IDC_FLOWCTRL</font></td>
<td WIDTH="44%"><font SIZE="3"><p ALIGN="JUSTIFY">标题为</font><font FACE="Times New Roman" SIZE="3">None</font><font SIZE="3">，选择</font><font FACE="Times New Roman" SIZE="3">Group</font><font SIZE="3">属性</font></td>
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<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">RTS/CTS</font><font SIZE="3">单选按钮</font></td>
<td WIDTH="26%"><font SIZE="3"><p ALIGN="JUSTIFY">缺省</font></td>
<td WIDTH="44%"><font SIZE="3"><p ALIGN="JUSTIFY">标题为</font><font FACE="Times New Roman" SIZE="3">RTS/CTS</font></td>
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<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">XON/XOFF</font><font SIZE="3">单选按钮</font></td>
<td WIDTH="26%"><font SIZE="3"><p ALIGN="JUSTIFY">缺省</font></td>
<td WIDTH="44%"><font SIZE="3"><p ALIGN="JUSTIFY">标题为</font><font FACE="Times New Roman" SIZE="3">XON/XOFF</font></td>
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<td WIDTH="29%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">TTY options</font><font SIZE="3">组框</font></td>
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