通过 TCP 套接字发送和接收数据的问题

Question

我在尝试使用我的 android (Basic4Android) 与运行 .net TCP 服务器的 PC 通信时遇到问题。我需要能够拥有向服务器发送 4 字节命令并接收响应的按钮。当我在android上运行程序时，服务器确实连接并接收到字符串“INFO”，但在我重新启动程序之前没有其他任何发送或接收，它只再次发送命令“INFO”。当我按下按钮发送命令时，我没有收到任何错误，但服务器从未收到任何内容。服务器是一个用VB.NET编写的Windows窗体多线程程序。我编写了一个可以工作的 VB.NET 客户端程序，我可以附上它作为我正在尝试做的事情的示例。这是我第一次尝试 Android 应用程序，到目前为止，我只是在修改教程中找到的网络示例。

代码如下... 谢谢

Sub Process_Globals
    Dim Socket1 As Socket
End Sub

Sub Globals
    Dim Button_ARM As Button
    Dim Button_STAY As Button
    Dim Button_AUTO As Button
    Dim Button_OFF As Button
    Dim Label_Received As Label
    Dim Label_Sent As Label
    Dim tr As TextReader 
    Dim tw As TextWriter
    Dim sb As StringBuilder
End Sub

Sub Activity_Create(FirstTime As Boolean) 
    Activity.LoadLayout("Alarm_Control")
    Socket1.Initialize("Socket1") 
    Socket1.Connect("#.#.#.#" , 8000, 20000)   'My IP address goes here
End Sub

Sub Socket1_Connected (Successful As Boolean) 
    If Successful = False Then 
        Msgbox(LastException.Message, "Error connecting") 
        Return 
    End If 
    tr.Initialize(Socket1.InputStream)
    tw.Initialize(Socket1.OutputStream)
    tw.WriteLine("INFO")
    Label_Sent.Text = "Sent INFO"
    tw.Flush    
    sb.Initialize
    sb.Append(tr.ReadLine) 
    Label_Received.Text = sb.ToString
    'Socket1.Close
End Sub 

Sub Button_ARM_Click 
    tw.WriteLine("O001")
    tw.Flush
    Label_Sent.Text = "Sent O001"
End Sub

Sub Button_STAY_Click
    tw.WriteLine("O002")
    tw.Flush
    Label_Sent.Text = "Sent O002"
End Sub

Sub Button_OFF_Click
    tw.WriteLine("O000")
    tw.Flush
    Label_Sent.Text = "Sent O000"
End Sub

Answer 1

你是如何读取服务器端的数据的？请注意，TextWriter.WriteLine 写入以 chr(10) 结尾的行。确保您没有在等待 chr(13) 和 chr(10)。

Answer 2

我在侦听器调用的线程中使用networkStream.read 和networkStream.write。 vb.net 客户端程序与 vb.net 服务器正常工作。

Public Sub handlerThread()
    Dim handlerSocket As Socket
    handlerSocket = alSockets(alSockets.Count - 1)
    Dim networkStream As NetworkStream = New NetworkStream(handlerSocket)
    Dim bytes(4) As Byte
    networkStream.Read(bytes, 0, CInt(4))        ' Read the stream into 4-byte array
    Dim clientdata As String = Encoding.ASCII.GetString(bytes) 
    Label_Received.Text = clientdata
    Dim responseString As String = "Received " + clientdata
    Dim sendBytes As [Byte]() = Encoding.ASCII.GetBytes(responseString)
    networkStream.Write(sendBytes, 0, sendBytes.Length)
    Label_Sent.Text = responseString
    handlerSocket = Nothing
End Sub

Answer 3

Chr(10) 在这里似乎不是问题。 我在使用这个 java 服务器代码时遇到了同样的问题：

import java.io.*;
import java.net.*;

public class ec192 {
  public static void main(String[] args) throws IOException {

    Socket echoSocket = null;
    PrintWriter out = null;
    BufferedReader in = null;

    try {

  echoSocket = new Socket("192.168.0.45", 2222);
      out = new PrintWriter(echoSocket.getOutputStream(), true);
      in = new BufferedReader(new InputStreamReader(
                              echoSocket.getInputStream()));
    } catch (UnknownHostException e) {
      System.err.println("Don't know about host: taranis.");
      System.exit(1);
    } catch (IOException e) {
      System.err.println("Couldn't get I/O for "
                         + "the connection to: 2222 taranis.");
      System.exit(1);
    }

BufferedReader stdIn = new BufferedReader(
                               new InputStreamReader(System.in));
String userInput;

    while ((userInput = stdIn.readLine()) != null) {
    out.println(userInput);
    System.out.println("echo: " + in.readLine());
}

out.close();
in.close();
stdIn.close();
echoSocket.close();
  }
}