.net - 通过TCP套接字发送JPEG ...有时不完整

Question

Vb.net

你好

我已经在一个项目上工作了几个月(vb 2008 express)。最后一个问题
我无法解决。

我需要将图像从“服务器”(监听器)发送到客户端。以下代码在大多数情况下都有效，但是有时图像不完整。我相信这可能与tcp数据包大小的变化有关，可能受网络上繁忙程度的限制。一世
我已经看到了将图像拆分为多个块并将其发送出去的代码示例，但由于我使用的是不同的vb版本，所以我无法使它们正常工作。要发送的图片最大不超过20k。

任何有效的代码示例都将是很棒的。数周来，我一直在尝试并没有克服最后的障碍。

谢谢您的期待。

客户 - - -

Sub GetPic()


        '------- Connect to Server
        ClientSocket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, _ ProtocolType.Tcp)
        ClientSocket.Connect(Epoint)

        '------- Send Picture Request
        Dim Bytes() As Byte = System.Text.ASCIIEncoding.ASCII.GetBytes("Send Picture")
        ClientSocket.Send(Bytes, Bytes.Length, SocketFlags.None)

        '------- Receive Response
        Dim RecvBuffer(20000) As Byte
        Dim Numbytes As Integer

        Numbytes = ClientSocket.Receive(RecvBuffer)

        Dim Darray(Numbytes) As Byte
        Buffer.BlockCopy(RecvBuffer, 0, Darray, 0, Numbytes)

        '------- Close Connection
        ClientSocket.Shutdown(SocketShutdown.Both)
        ClientSocket.Close()

        '-------
        Dim MStrm = New MemoryStream(Darray)
        Picture = Image.FromStream(MStrm)


End Sub

听众-----

'Threaded from a listener


    Sub ClientThread(ByVal Client As TcpClient)

        Dim MStrm As New MemoryStream
        Dim Rbuffer(1024) As Byte
        Dim Tbyte As Byte()
        Dim NStrm As NetworkStream = Client.GetStream()

        Dim I As Integer = NStrm.Read(Rbuffer, 0, Rbuffer.Length)
        Dim Incoming As String = System.Text.Encoding.ASCII.GetString(Rbuffer, 0, I)

        If Incoming = "Send Picture" then
                    Picture Save(MStrm, Picture.RawFormat)
                    Tbyte = MStrm.ToArray
                    NStrm.Write(Tbyte, 0, Tbyte.Length)
              End if

        Client.Close()

End Sub

Answer 1

这样获取图像的方式是完全错误的:

Numbytes = ClientSocket.Receive(RecvBuffer)

您很有可能会获得部分数据，因为套接字实际上在缓冲区中的容量可能小于完整镜像的数量。无论如何，尝试像这样接收它(我将在C#中给出示例):

MemoryStream responseStream = new MemoryStream();
byte[] recvBuffer = new recvBuffer[4096]; // just some size
int read = 0; // indicates how much data actually read from socket, can be smaller then buffer
do{
    read = ClientSocket.Receive( recvBuffer ); // recieve data
    responseStream.write( recvBuffer, 0, read ); // write it to resposne stream for later use
}
while( read != 0 );

这应该可以工作，但是在您的情况下，我会采取其他方法。这是客户的代码:

Socket s = new Socket( blablabla );
s.Connect( endPoint );
NetworkStream clientStream = new NetworkStream(s);
clientStream.Write( "Send picture" ); // send a command to server

int pictureSize = clientStream.ReadInt(); // here we expect to read following picture's size
byte[] pictureBuffer = clientStream.ReadBytes( pictureSize );

和服务器，监听器部分:

Socket serverSocket = new Socket( blablabla );
serverSocket.Bind( blabla );
serverSocket.Listen( 100 );

while( true ){
    Socket clientSocket = serverSocket.Accept();
    Thread t = new Thread( new ParametrizedThreadStart( (object Obj) =>
    {
        Socket clientSocket = (Socket)Obj;
        NetworkStream clientStream = new NetworkStream( clientSocket );
        string command = clientStream.ReadString();
        if( command == "Send picture" ){
            // get ur picture here
            // get it's size
            clientStream.Write( pictureSize );
            clientStream.Write( pictureBytes );
        }
    } ) );
    t.start( clientSocket );
}

我希望这段伪代码很清楚，可以随时提出问题:)