java中的TCP服务器和TCP客户端

Question

我正在尝试在我的 Spring Boot 应用程序中实现 TCP 服务器和客户端。 最初，我的控制器从另一个应用程序接收响应，在收到此响应时，我的服务类调用另一个方法来建立 tcp 连接。建立 tcp 连接后，我调用一个设置 tcp 客户端的方法。 TCP 服务器不断侦听来自已建立连接的机器的消息，并根据消息名称执行各种操作。每次执行代码时，都会出现以下错误：

java.net.BindException: Address already in use: JVM_Bind
    at java.net.DualStackPlainSocketImpl.bind0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketBind(DualStackPlainSocketImpl.java:106)
    at java.net.AbstractPlainSocketImpl.bind(AbstractPlainSocketImpl.java:387)
    at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:190)
    at java.net.ServerSocket.bind(ServerSocket.java:375)
    at java.net.ServerSocket.<init>(ServerSocket.java:237)
    at java.net.ServerSocket.<init>(ServerSocket.java:128)
    at com.epbRestServer.tcp.TCPServer.setupTCPConnection(TCPServer.java:24)
    at com.epbRestServer.service.impl.EPBRestServerServiceImpl.handleStartEPC(EPBRestServerServiceImpl.java:28)
    at com.epbRestServer.controller.EPBRestServerController.startEPC(EPBRestServerController.java:27)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:87)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

调用tcp客户端和tcp服务器方法的代码：

public ResponseBean handleStartEPC(RequestBean request) {
    // Code for establishing tcp connection
    ResponseBean response = new ResponseBean();

    if (request != null) {
        TCPServer tcpServer = new TCPServer();
        response = tcpServer.setupTCPConnection(request);
        if (response.getTcpConnect()) {
            TCPClient tcpClient = new TCPClient();
            TCPRequestBean tcpBean = new TCPRequestBean();
            String str = new String();
            str = str.concat("IP:").concat(request.getIpAddress()).concat(",NodeName:").concat(request.getVduName())
                    .concat(",Interface:").concat(request.getInterfaceName());
            int length = str.length();
            str = "Length:" + length +"," + str;
            tcpBean.setIpAddress(request.getIpAddress());
            tcpBean.setInputData(str);
            response = tcpClient.setupTCPClient(tcpBean);
        }

        else {
            response.setStatus("FAILURE");
        }

    }

    else {
        response.setStatus("FAILURE");
    }

    return response;
}

tcp客户端和tcp服务器的代码

public class TCPServer {

    @Autowired
    EPBRestServerService epbRestServerService;

    public ResponseBean setupTCPConnection(RequestBean request) {

        ResponseBean response = new ResponseBean();
        try {
            ServerSocket server = new ServerSocket(8000);
            Socket s = server.accept();// establishes connection
            DataInputStream dis = new DataInputStream(s.getInputStream());
            String str = (String) dis.readUTF();
            VNFNotificationRequestBean vnfRequestBean = new VNFNotificationRequestBean();
            System.out.println("message:" + str);
            switch (str.toLowerCase()) {
            case "restAPIResponse":
                response.setTcpConnect(true);
                response.setStatus("SUCCESS");
                break;
            case "startsuccess":
                vnfRequestBean.setEvent("StartSuccess");
                vnfRequestBean.setSystemId(request.getSystemId());
                vnfRequestBean.setContent("ContentType - application/json");
                response = epbRestServerService.triggerEvent(request, vnfRequestBean);
                break;
            case "initsuccess":
                vnfRequestBean.setEvent("InitSuccess");
                vnfRequestBean.setSystemId(request.getSystemId());
                vnfRequestBean.setContent("ContentType - application/json");
                response = epbRestServerService.triggerEvent(request, vnfRequestBean);
                break;
            case "configuresuccess":
                vnfRequestBean.setEvent("ConfigureSuccess");
                vnfRequestBean.setSystemId(request.getSystemId());
                vnfRequestBean.setContent("ContentType - application/json");
                response = epbRestServerService.triggerEvent(request, vnfRequestBean);
                break;
            default:
                response.setStatus("FAILURE");
                break;
            }
            server.close();
        } catch (IOException e) {
            response.setTcpConnect(false);
            e.printStackTrace();
        }
        return response;

    }

    public class TCPClient {

        public ResponseBean setupTCPClient(TCPRequestBean request) {

            ResponseBean response = new ResponseBean();
            try {
                Socket s = new Socket(request.getIpAddress(), 8000);
                DataOutputStream dout = new DataOutputStream(s.getOutputStream());
                dout.writeUTF(request.getInputData());
                dout.flush();
                dout.close();
                s.close();
                response.setStatus("SUCCESS");
            } catch (IOException e) {
                System.out.println(e);
                response.setStatus("FAILURE");
            }
            return response;
        }

    }

Answer 1

我不想粗鲁，但您的所有回复都基于“关键字”。并且应用程序本身正在阻止您尝试使用的网络端口。使用调用服务器端可访问的实际函数的 TCPClient 会容易得多，您甚至可以传递参数并获取返回值。它更加灵活和可靠。

这是 TCPServer 代码：

public class TCPServer {
/**
 * Class Constants
 */
public static int TCP_CLIENTS_INFINITE = 0;

/**
 * Class Variables
 */
private int serverPort; // Port on which the server will listen for incoming connections
private String serverIP; // IP that the server will be listening on
private int maxClients; // If set to 0 the max client amount is infinite
private int threadCount; // Displays the current amount of running TCP threads, can be interpreted as amount of connected clients
private Class classInstance; // Instance of a class that contains the functions needed for the server to operate
private boolean serverWorking = false; // Indicates if the server is online

/**
 * Class Functions
 */
private ServerSocket serverSocket;

/**
 * TCPServer class constructor
 *
 * @param serverPort           Port on which the server will listen to for incoming connections
 * @param maxClients           Maximum number of connected clients
 * @param serverFunctionsClass Class which contains all the server functions
 */
public TCPServer(int serverPort, int maxClients, Class serverFunctionsClass) {
    try {

        this.serverPort = serverPort;
        System.out.println("Server port has been set to: " + serverPort);
        this.maxClients = maxClients;
        System.out.println("Max connected clients has been set to: " + maxClients);
        this.classInstance = serverFunctionsClass;
        System.out.println("Server functions class has been set");
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

/**
 * Bind the TCP Server Socket to a specific ip address
 *
 * @param ip String representation of an IP Address
 */
public void bindSocketToIP(String ip) {
    try {
        this.serverIP = ip;
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

/**
 * Start the server and begin listening for connections
 */
public void start() {
    try {
        if (!serverWorking) {

            if (serverIP != null) {
                serverSocket = new ServerSocket(serverPort, 50, InetAddress.getByName(serverIP));
            } else {
                serverSocket = new ServerSocket(serverPort);
            }
            System.out.println("TCP Server is now listening for new connections, on port: " + serverSocket);

            serverWorking = true;

            if (maxClients == 0) {
                maxClients = 999;
            }

            while (true) {
                // Open Client socket to handle client connections
                Socket clientSocket = serverSocket.accept();

                if (clientSocket != null && getThreadCount() < getMaxClients()) {
                    new Thread(() -> new TCPClientHandler(clientSocket)).start();
                } else {
                    System.out.println(String.format("Exceeded maximum connected clients limit: %d / %d", getThreadCount(), getMaxClients()));
                }
            }
        } else {
            return;
        }
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

/**
 * Stop the server
 */
public void stop() {
    try {
        serverSocket.close();
        serverWorking = false;
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

/**
 * @return Current amount of connected clients a.k.a running threads
 */
public synchronized int getThreadCount() {
    return threadCount;
}

/**
 * @return Defined number of maximum clients accepted by the server at any given time
 */
public synchronized int getMaxClients() {
    return maxClients;
}


/**
 * Class which processes the client requests
 */
class TCPClientHandler {

    /**
     * Handle Client in a separate thread
     *
     * @param clientSocket TCP ServerSocket instance
     */
    public TCPClientHandler(Socket clientSocket) {

        // Inner Variables
        String clientSentence = null, clientIP = null;
        ObjectOutputStream toClient = null;
        ObjectInputStream fromClient = null;
        Object[] argumentsObjectArray;
        ArrayList argumentsCollectionArray;

        try {
            if (clientSocket.isConnected() && !clientSocket.isClosed()) {

                // Incline the threadNumber
                threadCount++;

                // Get connection input stream
                fromClient = new ObjectInputStream(clientSocket.getInputStream());

                // Get connection output stream
                toClient = new ObjectOutputStream(clientSocket.getOutputStream());

                while (true) {
                    try {
                        // Process fromClient
                        argumentsObjectArray = (Object[]) fromClient.readObject();

                        // Read client sentence
                        clientSentence = (String) argumentsObjectArray[0];

                        // Remove the client Sentence from argument array
                        argumentsCollectionArray = new ArrayList(Arrays.asList(argumentsObjectArray));
                        Collection c = argumentsCollectionArray;
                        c.remove(clientSentence);
                        argumentsObjectArray = c.toArray();

                        // Print was was received by the server
                        System.out.println("Function to be invoked: '" + clientSentence + "'");

                        for (Object o : argumentsObjectArray) {
                            System.out.println("Parameter: '" + o + "' Type: '" + o.getClass().getTypeName() + "'");
                        }

                        // Get Client IP Address
                        clientIP = clientSocket.getInetAddress().toString();

                        // Write data to client
                        toClient.writeObject(processServerFunction(clientSentence, argumentsObjectArray));
                    } catch (Exception ex) {
                        System.out.println("Connection with client: " + clientIP + ", has been terminated, closing sockets..." + '\n');
                        if (clientSocket != null) {
                            try {
                                clientSocket.close();
                            } catch (Exception e) {
                                // DO NOTHING
                            }
                        }
                        if (fromClient != null) {
                            try {
                                fromClient.close();
                            } catch (Exception e) {
                                // DO NOTHING
                            }
                        }
                        if (toClient != null) {
                            try {
                                toClient.close();
                            } catch (Exception e) {
                                // DO NOTHING
                            }
                        }
                        threadCount--;
                        break;
                    }

                }
            }
        } catch (Exception ex) {
            try {
                System.out.println("Connection with client: " + clientIP + ", has been terminated, closing sockets..." + '\n');
                if (clientSocket != null) {
                    try {
                        clientSocket.close();
                    } catch (Exception e) {
                        // DO NOTHING
                    }
                }
                if (fromClient != null) {
                    try {
                        fromClient.close();
                    } catch (Exception e) {
                        // DO NOTHING
                    }
                }
                if (toClient != null) {
                    try {
                        toClient.close();
                    } catch (Exception e) {
                        // DO NOTHING
                    }
                }
                threadCount--;
                ex.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Process Server Function, by it's String name
     *
     * @param functionName Name of the function or method interpreted as a String
     * @param args         Array of objects that which represent both function name and it's arguments if any
     * @return String value received from a invoked function
     */
    public Object processServerFunction(String functionName, Object[] args) {
        try {

            Method functionInvoker;
            Object clientEcho;

            if (args.length >= 1) {
                functionInvoker = classInstance.getDeclaredMethod(functionName, getParameterTypes(classInstance, functionName));
                clientEcho = functionInvoker.invoke(classInstance, args);
            } else {
                functionInvoker = classInstance.getDeclaredMethod(functionName);
                clientEcho = functionInvoker.invoke(classInstance);
            }

            if (clientEcho != null) {
                System.out.println("Sending to client: " + clientEcho);
            }
            return clientEcho;
        } catch (Exception ex) {
            ex.printStackTrace();
            System.out.println("Client requested function does not exists on the server");
            return "Client requested function does not exists on the server";
        }
    }

    /**
     * Get all the function parameter types dynamically
     *
     * @param aClass     class in which the function is located
     * @param methodName function name
     * @return Class[] of parameter types
     */
    private Class<?>[] getParameterTypes(Class<? extends Object> aClass, String methodName) {
        try {
            for (Method m : aClass.getDeclaredMethods()) {
                if (m.getName().equals(methodName)) {
                    return m.getParameterTypes();
                }
            }

            // If nothing have been found return null value
            return null;

        } catch (Exception ex) {
            ex.printStackTrace();
            return null;
        }
    }
}

这是 TCPClient 代码：

public class TCPClient {
/**
 * Variables
 */
private String serverIP;
private int serverPort;
private Socket clientSocket;
private boolean connected = false;
private ObjectOutputStream outToServer;
private ObjectInputStream inFromServer;

/**
 * Class constructor
 *
 * @param serverIP   String value that's representing the server ip
 * @param serverPort Integer value that represents server port
 */
public TCPClient(String serverIP, int serverPort) {
    try {
        this.serverIP = serverIP;
        this.serverPort = serverPort;
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

/**
 * Establish connection with the specified TCP server
 */
public void connect() {
    try {
        if (!connected) {
            try {
                System.out.println(String.format("Trying to connect to: %s on port: %d", getServerIP(), getServerPort()));
                clientSocket = new Socket(getServerIP(), getServerPort());
                System.out.println("Connected !");
                connected = true;
                // Create ObjectStreams
                outToServer = new ObjectOutputStream(clientSocket.getOutputStream());
                inFromServer = new ObjectInputStream(clientSocket.getInputStream());
            } catch (Exception e) {
                connected = false;
                if (clientSocket != null) {
                    clientSocket.close();
                    System.out.println(String.format("Could not connect to: %s on port: %d", getServerIP(), getServerPort()));
                }
            }
        } else {
            return;
        }
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

/**
 * Disconnect client for the currently connected server
 */
public void disconnect() {
    try {
        if (connected) {
            clientSocket.close();
            connected = false;
        }
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

/**
 * Invoke server side functions
 *
 * @param serverSideFunction Object representing both function name and its parameters
 * @return String vale of a server side function return value
 */
public Object invokeFunction(Object[] serverSideFunction) {
    try {
        if (clientSocket != null && connected) {
            outToServer.writeObject(serverSideFunction);
            Object modifiedSentence = inFromServer.readObject();
            if (modifiedSentence != null) {
                System.out.println("Received from server: " + modifiedSentence);
            }
            return modifiedSentence;
        }
        return null;
    } catch (Exception ex) {
        ex.printStackTrace();
        return null;
    }
}

/**
 * Get server ip data
 *
 * @return String value of Server IP
 */
public String getServerIP() {
    return serverIP;
}

/**
 * Get server port data
 *
 * @return Integer value of Server Port
 */
public int getServerPort() {
    return serverPort;
 }

使用方法如下：

1. 创建一个包含所有服务器端函数和方法的类，将其命名为 MyFuntions 或其他名称
   1. 创建 TCPServer 实例并提供所需数据，然后在新线程上启动服务器
   2. 创建 TCPClient 实例，提供所有数据并调用 .connect()
   3. 使用 TCPClient.invokeFunction() 调用服务器端函数

示例代码如下：

// This is how you start the server, yes it's that simple, just don't start it //everytime you call a function. Start it once.

TCPServer tcpServer = new TCPServer(6969, 0, MyFuntions.class);

new Thread(() -> {
   tcpServer.start();
}).start();


// Now create a TCPClient instance
TCPClient tcpClient = new TCPClient("Server IP as String", 6969);

tcpClient.connect(); // You can call it in a different Thread if you want

/*
Now lets say you have a server side function that's called: 'doMath(int x, int y)'

what you want to do to call it, and pass parameters is quite simple:
*/

tcpClient.invokeFunction(new Object[]{"doMath", 5, 10);

/*
The server will invoke this function do what you wanted with those number 
and if you want to return the outcome to the client it will do so aswell.

Just remember that the server-side functions and methods have to be public 
and static
*/

代码应该可以工作，我是使用 Notepad++ 编写的，所以这就是为什么异常>有点通用，因为我不记得在没有 IDE 的情况下应该使用哪个。