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我正在尝试编写一个充当中继服务器的打印机服务器，以从网络上的 JPOS 应用程序接收和发送连接，并将它们中继到网络上的打印机。

我正在使用 EPSON JPOS 工具进行测试，因为我有一台 EPSON 收据打印机。

使用 Java，现在我能够正确接收和发送 UDP 连接，但是对于 TCP 连接，我无法从 TCP 服务器读取任何内容；因为它几乎立即在 JPOS 应用程序中给出错误“端口已打开”，并且似乎关闭了与服务器的连接。

以下是 TCP 服务器套接字的代码：-

public class TcpListener {

    private int sendReceiveBufferSize = 256;

    public void listen(int port, int bufferSize) throws Exception {

        System.out.println("-- Running TCP Server at " + InetAddress.getLocalHost() + ":" + port + " --");

        ServerSocket serverSocket = null;

        try {
            serverSocket = new ServerSocket(port);
        } catch (IOException ex) {
            System.out.println("Can't setup server on this port number. ");
        }

        Socket jposSocket = null;
        InputStream inJpos = null;
        OutputStream outJpos = null;
        ByteArrayOutputStream abOutputStream = null;
        ByteArrayOutputStream abJposOutputStream = null;

        try {
            jposSocket = serverSocket.accept();
            jposSocket.setSoTimeout(5000);
            jposSocket.setReceiveBufferSize(sendReceiveBufferSize);
            jposSocket.setSendBufferSize(sendReceiveBufferSize);
        } catch (IOException ex) {
            System.out.println("Can't accept client connection. ");
        }

        try {
            inJpos = jposSocket.getInputStream();
        } catch (IOException ex) {
            System.out.println("Can't get socket input stream. ");
        }

        try {
            outJpos = jposSocket.getOutputStream();
        } catch (IOException ex) {
            System.out.println("Can't get socket input stream. ");
        }

        abOutputStream = null;
        abJposOutputStream = new ByteArrayOutputStream();

        Socket printerSocket = null;
        InputStream inPrinter = null;
        OutputStream outPrinter = null;

        int count = 0;

        while (true)
        {
            abOutputStream = new ByteArrayOutputStream();
            byte[] bytes = new byte[bufferSize];

            //count = inJpos.read(bytes);

            while (true) {
                if (inJpos.available() > 0)
                {
                    count = inJpos.read(bytes);
                    abOutputStream.write(bytes, 0, count);

                    break;
                }
                else {
                    Thread.sleep(1000);
                }
            }

            System.out.println(port + " TCP --> " +  abOutputStream.toString("UTF-8"));

                if (printerSocket == null)
                {
                    printerSocket = new Socket("192.168.10.31", port);

                    inPrinter = printerSocket.getInputStream();
                    outPrinter = printerSocket.getOutputStream();
                }

                outPrinter.write(abOutputStream.toByteArray());

                bytes = new byte[bufferSize];

                while (inPrinter.available() > 0 && (count = inPrinter.read(bytes)) > 0) {
                    abJposOutputStream.write(bytes, 0, count);
                }

                outJpos.write(abJposOutputStream.toByteArray());
                outJpos.flush();
        }
    }
}

然后在一个单独的线程上从 Main 应用程序调用 Listen 方法。

上面的代码在使用我编写的客户端进行测试时工作正常，它可以正确发送和接收消息，但问题在于 JPOS 连接。

对来自 JPOS 应用程序的 TCP 连接是否有某种特殊处理？

任何帮助，将不胜感激。

谢谢

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