如何保持TCP套接字打開？

Question

我們的應用程序具有與許多服務器的類似乒乓的對話（每個服務器都有一個用於建立這些連接的對應線程）。 下面的代碼可以工作，但是它為每個新請求打開一個新連接，並且只能使用一次，這很快就會達到服務器設置的最大連接上限。

DataProvider.java

public static ZnResult sendTcpQuery(String xml, String url, int port) {
    List<ZnXmlResult> results = new ArrayList<>();
    String xmlString = xml != null ? new String((xml + "\n").getBytes()) : "";
    int error = ZnResult.OK;
    try (Socket clientSocket = new Socket(url, port)) {
        clientSocket.setSoTimeout(CONNECTION_TIMEOUT);
        DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
        try (BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream(), "UTF-8"))) {
            outToServer.writeBytes(xmlString);
            try (StringWriter responseFromServer = new StringWriter()) {
                String readLine;
                while ((readLine = inFromServer.readLine()) != null) {
                    ...
                }
            }
            outToServer.close();
            clientSocket.close();
        }
    } catch (Exception ex) {
        LOG.error("Exception {}", url + ":" + port, ex);
        error = ZnResult.ERR;
    }
    return error == ZnResult.OK ? new ZnResult(results) : new ZnResult(error);
}

如何轉換它，以便所有事情都可以在一個連接中完成？ 我想我會做這樣的事情：

SocketFactory.java

public class SocketFactory {
private static HashMap<String, Socket> socketsByAddress = new HashMap<>();
private static HashMap<Socket, DataOutputStream> outputStreamsBySocket = new HashMap<>();
private static HashMap<Socket, BufferedReader> readersBySocket = new HashMap<>();

public static Socket getSocket(String address) {
    String ip = Tools.getIpFromAddress(address);
    int port = Tools.getPortFromAddress(address);
    Socket socket = socketsByAddress.get(address);
    if (socket == null) {
        try {
            socket = new Socket(ip, port);
            socket.setSoTimeout(60000);
            socketsByAddress.put(address, socket);
        } catch (IOException ex) {
            Logger.getLogger(SocketFactory.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    return socket;
}

public static DataOutputStream getOutputStream(Socket socket) {
    DataOutputStream outputStream = outputStreamsBySocket.get(socket);
    if (outputStream == null) {
        try {
            outputStream = new DataOutputStream(socket.getOutputStream());
            outputStreamsBySocket.put(socket, outputStream);
        } catch (IOException ex) {
            Logger.getLogger(SocketFactory.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    return outputStream;
}

public static BufferedReader getReader(Socket socket) {
    BufferedReader reader = readersBySocket.get(socket);
    if (reader == null) {
        try {
            reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            readersBySocket.put(socket, reader);
        } catch (IOException ex) {
            Logger.getLogger(SocketFactory.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    return reader;
}
}

DataProvider.java

public static ZnResult sendTcpQuery(String xml, String url, int port) {
    List<ZnXmlResult> results = new ArrayList<>();
    int error = ZnResult.OK;
    try {
        String xmlString = xml != null ? new String((xml + "\n").getBytes()) : "";
        Socket clientSocket = SocketFactory.getSocket(url + ":" + port);
        DataOutputStream outToServer = SocketFactory.getOutputStream(clientSocket);
        BufferedReader inFromServer = SocketFactory.getReader(clientSocket);
        outToServer.writeBytes(xmlString);
        try (StringWriter responseFromServer = new StringWriter()) {
            String readLine;
            while ((readLine = inFromServer.readLine()) != null) {
                ...
            }
        }
    } catch (Exception ex) {
        LOG.error("Exception {}", url + ":" + port, ex);
        error = ZnResult.ERR;
    }
    return error == ZnResult.OK ? new ZnResult(results) : new ZnResult(error);
}

但是它只是行不通，只有第一個通過。

Answer 1

該循環讀取直到流結束。

while ((readLine = inFromServer.readLine()) != null) {

流僅結束一次。 即您不能結束流，但是稍后再使用它。

您需要做什么？

• 有一個終結行，該終結行不會出現在您的數據中。 例如，等待"[EOF]"
• 首先發送數據長度，僅讀取那么多數據。

Answer 2

嘗試像第一個代碼中那樣使用URL而不是IP地址來初始化Socket對象，然后查看它是否對您有用。