我需要制作一个TCP服务器，该服务器接受来自客户端的套接字并从它们接收数据，并将接收到的数据发送给所有客户端。为此，我的Server类将接受的连接保存到ArrayList<Socket>，并且希望将数据发送到客户端：
Arraylist<Socket> sockets=Server.getSockets();
for(Socket current: sockets)
{
ObjectOutputStream out=new ObjectOutputStream (current.getOutputStream());
out.flush();
out.writeObject(object);
out.flush();
out.close();
}
但这不起作用。怎么了？
最佳答案
您的代码段没有错，我唯一能感觉到的问题是客户端代码的实现方式。假设您的客户代码是这样的。
Socket clientSocket = new Socket(ip, port);
BufferedReader inFromUser = new BufferedReader( new InputStreamReader(System.in));
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
while ( true ){
String sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + '\n');
outToServer.flush();
DataInputStream is = new DataInputStream(clientSocket.getInputStream());
System.out.println(is.readLine());
}
现在，此客户端正在从控制台读取输入，并将其发送到服务器，然后将其张贴以等待响应。假设服务器将在接收到“ fire”消息时将数据发送给所有人[这是您想要的]。
现在有两个连接到服务器的客户端，即ClientA和ClientB。
1. ClientA blocked at user-input (console)
2. User enter 'abc'
3. ClientA moves on sends 'abc' to server
4. ClientA blocks to read data from server
5. Server sends back 'abc' to ClientA [Assuming its an echo server]
6. ClientA reads the data, print it
7. ClientA moves back(while loop), blocked again for user input.
ClientB也会发生相同的情况，因此现在都阻止了这两个操作，以防用户从控制台输入。
假设现在ClientA用户发送了我们的魔语[在这种情况下为'fire'，服务器识别出它是魔语并开始向ClientA和ClientB发送数据，
现在，这里要注意的重要一点是ClientA和ClientB的状态，这时ClientA刚发送数据，并在第4点，因此被阻止从服务器读取数据，因此，当服务器发送消息时，它可以读取和显示，而clientB在第1点，则阻止从控制台获取数据..因此，即使服务器已发送数据，ClientB也有要读取的数据，但是由于其停留在第1点而无法读取，因此您正在从以下位置关闭连接服务器在写入后运行，因此，如果ClientB在某种程度上从点1移到点4，则套接字已经关闭，因此它将再次无法读取。尽管服务器已将数据发送到ClientA和ClientB，但是只有ClientA能够获取它。
ew！很长的解释，我想它为您提供解决问题的指导
服务器代码供参考
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectOutputStream;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class BroadCastTCPServer {
private static ArrayList<Socket> sockets = new ArrayList<Socket>();
//Usage: java TCPServer port
public static void main(String args[]){
BroadCastTCPServer server = new BroadCastTCPServer();
try {
server.startServer("9999");
} catch (Exception e) {
e.printStackTrace();
}
}
private void startServer(String portStr) throws IOException {
int port = Integer.parseInt(portStr);
ServerSocket serverSocket = new ServerSocket(port);
System.out.println("Listening on IP:" + serverSocket.getInetAddress().getHostAddress() + " Port:"+port);
while(true){
Socket connectionSocket = serverSocket.accept();
sockets.add(connectionSocket);
System.out.println("New client connection:" + connectionSocket.getRemoteSocketAddress());
ClientHandler cl = new ClientHandler(connectionSocket);
Thread clientThread = new Thread(cl);
clientThread.start();
}
}
public void sendAll() throws Exception{
System.out.println("No of connections:" + sockets.size());
for(Socket current: sockets){
System.out.println(current.getRemoteSocketAddress());
ObjectOutputStream out=new ObjectOutputStream (current.getOutputStream());
out.flush();
out.writeObject("Tata\n");
out.flush();
//out.close();
}
}
class ClientHandler implements Runnable{
Socket socket;
public ClientHandler(Socket socket){
this.socket = socket;
}
@Override
public void run() {
BufferedReader inFromClient = null;
ObjectOutputStream out = null;
BufferedWriter br = null;
try {
inFromClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out=new ObjectOutputStream (socket.getOutputStream());
OutputStreamWriter or= new OutputStreamWriter(out);
br = new BufferedWriter(or);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
while(true){
String clientSentence= null;
try {
clientSentence = inFromClient.readLine() ;
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
System.out.println("Received: " + clientSentence);
if (clientSentence.equalsIgnoreCase("fire")) {
try {
sendAll();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}else{
try {
br.write(clientSentence + "\n" );
br.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}
}
关于java - Java TCP Server不会将数据发送到客户端，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/14647419/