串口编程之端口

软件程序与硬件通过串口交换数据，首先要知道com口，但是com口是由计算机动态随机分配的。也就是说com口的编号是变化的。因此我们在编程时不能将com的编号写死。针对此问题我们想到的可能是将所有com口读出来绑定到下拉框，软件启动后从下拉框选择需要的端口。或者写到配置文件，软件启动前在配置文件配置。不用说这两种方法都不是很理想。后来通过查询资料原来com口的变化会在注册表中记录。如图。

这样我们就有一个想法，能不能通过监控注册表来监测com口。于是有了下面代码。

  1 using microsoft.win32;
  2 using system;
  3 using system.threading;
  4 using system.threading.tasks;
  5 
  6 namespace autotester.utilities
  7 {
  8     public class comlistenservice
  9     {
 10         /// <summary>
 11         /// com监听服务类
 12         /// </summary>
 13         /// <param name="serialport">需要监听的端口</param>
 14         //public comlistenservice(string serialport)
 15         //{
 16         //    _serialport = serialport;
 17         //}
 18 
 19         /// <summary>
 20         /// 监听连接状态事件
 21         /// </summary>
 22         public event action<string, bool> connectionstatuschanged;
 23 
 24         /// <summary>
 25         /// 连接状态
 26         /// </summary>
 27         private bool _connectionstatus;
 28 
 29         /// <summary>
 30         /// 连接状态
 31         /// </summary>
 32         private bool connectionstatus
 33         {
 34             get { return _connectionstatus; }
 35             set
 36             {
 37                 if (_connectionstatus != value)
 38                 {
 39                     _connectionstatus = value;
 40                     connectionstatuschanged(_serialport, value);
 41                 }
 42             }
 43         }
 44 
 45 
 46         /// <summary>
 47         /// 开始监听
 48         /// </summary>
 49         public void startlisten()
 50         {
 51             _tokensource = new cancellationtokensource();
 52 
 53             task.factory.startnew(() =>
 54             {
 55                 listenning();
 56             });
 57         }
 58 
 59         /// <summary>
 60         /// 停止监听
 61         /// </summary>
 62         public void stoplisten()
 63         {
 64             _tokensource.cancel();
 65         }
 66 
 67         /// <summary>
 68         /// 监听端口
 69         /// </summary>
 70         public void listenning()
 71         {
 72             while (true)
 73             {
 74                 thread.sleep(listenfrequency);
 75 
 76                 if (_tokensource.iscancellationrequested)
 77                 {
 78                     break;
 79                 }
 80 
 81                 lock (_locker)
 82                 {
 83                     bool isexist = false;
 84                     registrykey keycom = registry.localmachine.opensubkey(@"hardware\devicemap\serialcomm");
 85                     if (keycom != null)
 86                     {
 87                         string[] ssubkeys = keycom.getvaluenames();
 88 
 89                         foreach (string sname in ssubkeys)
 90                         {
 91                             string svalue = string.empty;
 92 
 93                             //if (svalue == _serialport)
 94                             //{
 95                             //    isexist = true;
 96                             //    break;
 97                             //}
 98 
 99                             if (sname.contains("prolificserial") || sname.toupper().contains("vcp"))                           
100                             { 
101                                 _serialport = (string)keycom.getvalue(sname);
102                                 isexist = true;
103                                 break;
104                             }
105                         }
106                     }
107 
108                     connectionstatus = isexist;
109                 }
110             }
111         }
112 
113 
114         private string _serialport;
115         private cancellationtokensource _tokensource;
116         private const int listenfrequency = 1000; //监听频率(毫秒)
117         private static readonly object _locker = new object();
118     }
119 }

（注：prolificserial和vcp和你的硬件设备有关，插上你的硬件后观察注册表变化）

调用非常简单，直接上代码。

1  comlistenservice cls = new comlistenservice();
2  cls.connectionstatuschanged += cls_connectionstatuschanged;
3  cls.startlisten();

 1         /// <summary>
 2         /// 
 3         /// </summary>
 4         /// <param name="comport"></param>
 5         /// <param name="status"></param>
 6         private static void cls_connectionstatuschanged(string comport, bool status)
 7         {
 8             if (status)
 9             {
10                 //comport已插入
11             }
12             else
13             {
14                 //comport已拔出
15             }
16         }

测试后，完美一切正常。