C# 串口通信问题（提示：端口被关闭）

[一条路坚持下去]

string ls = null;
/// <summary>
/// 根据开阀度数打开阀门
/// </summary>
/// <param name="ls_CmdType">指令类型</param>
/// <returns></returns>
private void SendCommand(string ls_CmdType,string ls_CmdTypeStr,int i)
{
DataTable dt = null;
string terstr = null;//临时数据表存储“H_Termina”
string ls_teradds = null;//变量TerAdds
string ls_str = null;//组合参数
//string ls_wk = null;//临时TerminalID
string ls_TerRemark = null;//该设备所属com口
try
{
if (ltvEmp.Items.Count > 0)
{

if (i == -1)
{
terstr = ltvEmp.SelectedItems[0].SubItems[1].Text;
}
else
{
terstr = ltvEmp.Items[i].SubItems[1].Text;
}
isml = terstr;
Reclb = 1;

dt = dbr.getTable("select TerAdds,TerRemark from H_Termina where TerminalID = '" + isml + "'");
ls_teradds = dt.Rows[0][0].ToString();
ls_TerRemark = dt.Rows[0][1].ToString();
switch (ls_CmdType)//如果是开阀就按此格式添加
{
case "K"://开/关阀
ls_str = "I" + ls_teradds.Substring(ls_teradds.Length - 4, 4)
+ ls_TerRemark
+ isml.Substring(isml.Length - 2, 2)
+ ls_CmdType
+ ls_CmdTypeStr;
break;
case "J"://允许巡逻
ls_str = "I" + ls_teradds.Substring(ls_teradds.Length - 4, 4)
+ "000"
+ ls_CmdType;
break;
case "C"://禁止巡逻
ls_str = "I" + ls_teradds.Substring(ls_teradds.Length - 4, 4)
+ "000"
+ ls_CmdType;
break;
case "V"://检查温度
ls_str = "L" + ls_teradds.Substring(ls_teradds.Length - 4, 4)
+ ls_TerRemark
+ "FF"
+ ls_CmdType;
break;
case "T"://检查时间
ls_str = "L" + ls_teradds.Substring(ls_teradds.Length - 4, 4)
+ ls_TerRemark
+ "FF"

+ ls_CmdType;
break;
case "M"://置模式
ls_str = "I" + ls_teradds.Substring(ls_teradds.Length - 4, 4)
+ ls_TerRemark
+ isml.Substring(isml.Length - 2, 2)
+ ls_CmdType
+ ls_CmdTypeStr;
break;
case "H"://搜索汇接器指令1
ls_str = "I0000000J";
break;
case "H2"://搜索汇接器指令2
ls_str = "L0000000X";
break;
default:
ls_str = null;
break;
}

string model = protocol.Getinstance(ls_str)._Model;

756行 spPort.Write(model);//将指令写入串口缓冲区
dt.Clear();
dt.Dispose();

spPort.DiscardOutBuffer();//清理输出缓冲区
spPort.DiscardInBuffer();//清理输入缓冲区


//new protocol().Dispose();//释放类资源
//}

}
}
catch (System.Exception e)
{
MessageBox.Show(e.ToString(), "警告");
}

}

[一条路坚持下去]

void OpenComm() { if (spPort.IsOpen) { spPort.DataReceived -= new System.IO.Ports.SerialDataReceivedEventHandler(spPort_DataReceived); spPort.Close(); MessageBox.Show("please Connect"); this.Close(); } else { spPort.PortName = ClassPub.CommCOM; spPort.BaudRate = 9600; try { spPort.Open(); spPort.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(spPort_DataReceived); if (spPort.IsOpen) { MessageBox.Show(" 连接设备成功 ！"); } } catch (Exception ex) { if (MessageBox.Show(" 连接设备失败或重复连接设备，是否退出重新登录 ", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.None, MessageBoxDefaultButton.Button1) == DialogResult.OK) { spPort.Close(); } } } } 以及下面的 if (!spPort.IsOpen) { ---- ｝ 如何改才能解决

引用 7 楼 pfworld 的回复:

if (spPort.IsOpen) { spPort.DataReceived -= new System.IO.Ports.SerialDataReceivedEventHandler(spPort_DataReceived); spPort.Close(); ……

[yinghuigu]

ls_str=null了

[一条路坚持下去]

引用 9 楼 yinghuigu 的回复:

ls_str=null了

什么意思

[一条路坚持下去]

难道是字符串为空？

[一条路坚持下去]

高手在哪？？？？

[一条路坚持下去]

void OpenComm() { if (spPort.IsOpen) { spPort.DataReceived -= new System.IO.Ports.SerialDataReceivedEventHandler(spPort_DataReceived); spPort.Close(); MessageBox.Show("please Connect"); this.Close(); } else { spPort.PortName = ClassPub.CommCOM; spPort.BaudRate = 2400; try { spPort.Open(); spPort.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(spPort_DataReceived); if (spPort.IsOpen) { MessageBox.Show(" 连接设备成功 ！"); } } catch (Exception ex) { if (MessageBox.Show(" 连接设备失败或重复连接设备，是否退出重新登录 ", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.None, MessageBoxDefaultButton.Button1) == DialogResult.OK) { spPort.Close(); } } } } 这是定义串口的代码，是不是我不连接设备就提示：端口被关闭的错误，请指教

[快溜]

调试一下看看写入前spPort的端口状态，提示你写入时端口已经关了。

[zhpfaff]

在 spPort.Write(model);前加上如下代码，检查一下端口是否打开 if (！spPort.IsOpen) { OpenComm(); }

[一条路坚持下去]

引用 3 楼 zhpfaff 的回复:

在 spPort.Write(model);前加上如下代码，检查一下端口是否打开

if (！spPort.IsOpen)
{
OpenComm();
}

但是出现这样的错误

[一条路坚持下去]

上面那个截图错了，是这个错误

[一条路坚持下去]

高人来给看看啊

[pfworld]

if (spPort.IsOpen) { spPort.DataReceived -= new System.IO.Ports.SerialDataReceivedEventHandler(spPort_DataReceived); spPort.Close(); MessageBox.Show("please Connect"); this.Close(); } else { ---- ｝ 这里有问题，应该是： if (!spPort.IsOpen) { ---- ｝ 判断错了，应该是打开就继续，没有打开重新打开(或者退出返回)！

[warren_cao]

楼主解决没有？我遇到同样的问题了