java socket 打印机_socket.BeginReceive（）使打印机无响应

我一直在开发一个应用程序，它可以在到达时自动在特定网络打印机上打印PDF文件并监控 @PJL USTATUS JOB 消息 . 但是，每当我开始我的应用程序并且代码命中 socket.BeginReceive() 时，打印机就无法从任何工作站接收任何打印作业，这也意味着永远不会调用回调 . 但是，如果我关闭我的应用程序或仅关闭套接字，打印机将再次开始工作 .

我错过了什么吗？像阻塞/非阻塞或同步或异步套接字？

public class SocketData {

public Socket socket;

public byte[] dataBuffer = new byte[1024];

}

public void Start() {

// start the thread that checks the printer status

thread = new Thread(new ThreadStart(ConnectAndListen));

thread.Priority = ThreadPriority.Lowest;

thread.Start();

// start the file listener

listener = new FileSystemWatcher(this.WatchPath);

listener.Created += new FileSystemEventHandler(listener_Created);

listener.EnableRaisingEvents = true;

}

public void ConnectAndListen() {

ipEndPoint = new IPEndPoint(Dns.GetHostEntry(this.IPAddress).AddressList[0], 9100);

socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

socket.Connect(ipEndPoint);

//socket.Send(Encoding.ASCII.GetBytes("\x1B%-12345X@PJL USTATUS DEVICE = ON\r\n\x1B%-12345X\r\n"));

//socket.Send(Encoding.ASCII.GetBytes("\x1B%-12345X@PJL USTATUS JOB = ON\r\n\x1B%-12345X\r\n"));

socket.Send(Encoding.ASCII.GetBytes("\x1B%-12345X@PJL USTATUS PAGE = ON\r\n\x1B%-12345X\r\n"));

//socket.Send(Encoding.ASCII.GetBytes("\x1B%-12345X@PJL USTATUS TIMED = 0\r\n\x1B%-12345X\r\n"));

ListenForPrinterReadBack(socket);

}

public void ListenForPrinterReadBack(Socket socket) {

if (DataRecievedCallBack == null) {

DataRecievedCallBack = new AsyncCallback(OnDataReceived);

}

SocketData socketData = new SocketData();

socketData.socket = socket;

m_asynResult = socket.BeginReceive(socketData.dataBuffer, 0, socketData.dataBuffer.Length, SocketFlags.None, DataRecievedCallBack, socketData);

}

public void OnDataReceived(IAsyncResult asyn) {

SocketData socketData = (SocketData)asyn.AsyncState;

int result = socketData.socket.EndReceive(asyn);

char[] chars = new char[result + 1];

Decoder d = Encoding.UTF8.GetDecoder(); //creating object for decoding

int charLen = d.GetChars(socketData.dataBuffer, 0, result, chars, 0);

String recievedData = new String(chars);

this.Status = recievedData;

ListenForPrinterReadBack(socketData.socket);

}

我知道我可以进行民意调查，但我无法收到未经请求的打印机消息 .

提前致谢！

UPDATE: 我感觉打印机上只允许一个套接字连接 . 由于 socket.BeginReceive() 只能在连接套接字时才能工作，因此套接字已被使用，因此无法发送任何其他请求 . 也许有另一种方法来处理未经请求的打印机回读？