我已使用套接字实现了服务器和客户端。在那个多个客户端必须能够连接。
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>9.3-1102-jdbc4</version>
<scope>test</scope>
</dependency>
以下是客户端（传感器）的代码。
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
import java.util.Set;
import sensors.FireAlarmSensor;
public class SensorServer {
private static final int port = 9000;
private static HashMap<String, PrintWriter> fireSensorPrintersList = new HashMap<String, PrintWriter>();
private static HashMap<String,FireAlarmSensor> fireSensorsList = new HashMap<String,FireAlarmSensor>();
private static String sensorIDNumber;
private static double temperatureLevel;
private static double CO2Level;
private static double batteryLevel;
private static double smokeLevel;
public static void main(String args[]){
System.out.println("Sensor Server Is Running");
ServerSocket clientListener = null;
try {
clientListener = new ServerSocket(port);
new sensorHandler(clientListener.accept()).start();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally {
try {
clientListener.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static class sensorHandler extends Thread{
private String sensorID;
private Socket socket;
private BufferedReader receiver;
private PrintWriter sender;
public sensorHandler(Socket socket) {
this.socket = socket;
try {
this.receiver = new BufferedReader(new InputStreamReader(socket.getInputStream()));
this.sender = new PrintWriter(socket.getOutputStream(),true);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void run(){
while(true){
sender.println("REQUESTID");
try {
sensorID = receiver.readLine();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(sensorID == null){
System.out.println("Empty Sensor ID");
}
synchronized (fireSensorPrintersList) {
if(!fireSensorPrintersList.containsKey(sensorID)){
fireSensorPrintersList.put(sensorID,sender);
break;
}
}
}
sender.println("SENSORACCEPTED");
try{
while(true){
//Set<String> sensorIDList= fireSensorPrintersList.keySet();
/*for(PrintWriter writer:fireSensorPrintersList.values()){
sensorIDNumber = fireSensorsList.get(sensorIDList).getSensorID();
temperatureLevel = fireSensorsList.get(sensorIDList).getTemperatureLevel();
batteryLevel = fireSensorsList.get(sensorIDList).getBatteryLevel();
CO2Level = fireSensorsList.get(sensorIDList).getCO2Level();
smokeLevel = fireSensorsList.get(sensorIDList).getSmokeLevel();
}*/
/*try {
Thread.sleep(3000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}*/
}
}
finally {
try {
socket.close();
System.out.println("Sensor server closed");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}
服务器在我的程序中工作正常。它不会随时崩溃，第一个传感器也可以与服务器连接，它也永远不会崩溃。但是当尝试通过运行FireAlarmSensor.class文件将另一个传感器连接到服务器时，第二个传感器会给我以下异常并崩溃。
package sensors;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.Serializable;
import java.net.Socket;
import java.util.Scanner;
public class FireAlarmSensor implements Serializable{
BufferedReader lineIn;
PrintWriter lineOut;
private String sensorID = "Not Set";
private BatterySensor batterySensor;
private TemperatureSensor temperatureSensor;
private SmokeSensor smokeSensor;
private CO2Sensor co2Sensor;
public FireAlarmSensor(String sensorID){
this.sensorID = sensorID;
this.batterySensor = new BatterySensor();
this.temperatureSensor = new TemperatureSensor();
this.smokeSensor = new SmokeSensor();
this.co2Sensor = new CO2Sensor();
}
public FireAlarmSensor(){
/*JFrame frame = new JFrame();
frame.setSize(500, 500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);*/
}
public String getSensorID(){
return this.sensorID;
}
public double getBatteryLevel(){
return batterySensor.getSensorData();
}
public double getTemperatureLevel(){
return temperatureSensor.getSensorData();
}
public double getSmokeLevel(){
return smokeSensor.getSensorData();
}
public double getCO2Level(){
return co2Sensor.getSensorData();
}
public void run(){
String serverAddress = "localhost";
Socket socket = null;
try {
socket = new Socket(serverAddress,9000);
lineIn = new BufferedReader(new InputStreamReader(socket.getInputStream()));
lineOut = new PrintWriter(socket.getOutputStream(),true);
while(true){
String serverInput = lineIn.readLine();
if(serverInput.startsWith("REQUESTID")){
Scanner userInput = new Scanner(System.in);
System.out.print("Enter the Sensor ID : ");
String sensorID = userInput.nextLine();
lineOut.println(sensorID);
}
else if(serverInput.startsWith("SENSORACCEPTED")){
System.out.println("Sensor Is Accepted");
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
/*finally{
try {
socket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}*/
}
public static void main(String args[]){
FireAlarmSensor sensor = new FireAlarmSensor();
sensor.run();
}
}
我使用eclipse neon在同一台机器上运行服务器和所有传感器。
客户端（传感器）中16到27行会导致错误，因为我还没有上传那些java文件。请在运行时注释或删除它们。
答案 0 :(得分：0)
main方法只调用accept一次，因此只有一个客户端可以连接就不足为奇了。尝试循环接受客户端：
private static boolean shouldExit = false;
public static void main(String args[]) {
System.out.println("Sensor Server Is Running");
try (ServerSocket listener = new ServerSocket(port)) {
acceptLoop(listener);
} catch (IOException e) {
e.printStackTrace();
}
}
private static void acceptLoop(ServerSocket listener) throws IOException {
while (!shouldExit) {
// accept() blocks until a connection is made
Socket client = listener.accept();
new sensorHandler(client).start();
}
}
这样做只会永远循环，接受新客户，直到您将shouldExit设置为true。主线程，即。
我冒昧地使用Java 7 try-with-resources语句（try (ServerSocket listener = ...)）。它基本上完成了你的错综复杂的try-catch-finally所做的事情 - 自动关闭ServerSocket。