初次写JAVA 使用Socket的多线程的多人聊天出现服务端不能接收。

Question

用gui+socket写的，已实现服务端可以发送信息给客户端，客户端可以接收信息，
但客户端发给服务端却不能接收。只用了输入、输出流，没用多线程先。
刚学，没有写过，有很多不懂，希望有人能帮我看看出了什么错，谢谢！

类Server
package tcp_udp;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

import javax.swing.*;
public class Server extends JFrame{
static JTextArea w;
static JTextArea send1;
static String t1;//发送框里的内容
Server()
{
setTitle("服务器");
w=new JTextArea();
JButton send2=new JButton("发送");
send1=new JTextArea(3,8);
JPanel s1=new JPanel();
send2.addActionListener(new ActionListener()
{

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub

// Server.t1=send1.getText();
socket.prin(send1.getText());
}});
add(w,"Center");
s1.add(send1);
s1.add(send2);
add(s1,"South");
setVisible(true);
setSize(300,300);
setLocationRelativeTo(null);//窗口居中

}
public static void main(String[] args) {
    // TODO Auto-generated method stub
    new Server();
    socket q2=new socket();
    q2.start();
}

}

class socket extends Thread
{
ServerSocket s;
Socket s1;
static PrintStream p1;
BufferedReader in;
static String L2;
socket(){
try {
s=new ServerSocket(9984);
System.out.println("服务器开启：");
while(true)
{
s1=s.accept();
p1=new PrintStream(s1.getOutputStream());
in=new BufferedReader(new InputStreamReader(s1.getInputStream()));
L2=in.readLine();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace(); }
}
public void run()//接收
{

    //          String L2=in.readLine();
    if(L2!=null&&L2.trim()!="")
    {String n="[客户：]";
        new Add2(n,L2);

    }
}

static void prin( String t)//发送
{String n="";
    p1.println(t);
    new Add2(n,t);

}}

class Add2//将发送或接收的信息显示在文本框
{
Add2(String n,String L1)
{
Server.w.append(n+L1+"\n");
}}
类Cilent
package tcp_udp;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.net.Socket;

import javax.swing.*;

public class Cilent extends JFrame{
static JTextArea w;
static JTextArea send2;
Cilent()
{
setTitle("客户");
w=new JTextArea();
JButton send=new JButton("发送");
send2=new JTextArea(3,8);
JPanel s1=new JPanel();
send.addActionListener(new ActionListener()
{

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub
        Socket1.prin(send2.getText());
    }});

add(w,"Center");
s1.add(send2);
s1.add(send);
add(s1,"South");
setVisible(true);
setSize(300,300);
setLocationRelativeTo(null);//窗口居中

}
public static void main(String[] args) {
    // TODO Auto-generated method stub

    new Cilent();
    Socket1 q1=new Socket1();
    q1.start();
}}

class Add1//将发送或接收的信息显示在文本框
{
Add1(String n,String L1)
{
Cilent.w.append(n+L1+"\n");
}
}

class Socket1 extends Thread
{
static BufferedReader in1;
static PrintStream out;
static String L1;
Socket1(){
try {
Socket ss1=new Socket("127.0.0.1",9984);
in1=new BufferedReader(new InputStreamReader(ss1.getInputStream()));
out=new PrintStream(ss1.getOutputStream());
L1=in1.readLine();

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
static void prin( String t)//发送
{String n="";
out.println(t);
System.out.print(t+"hhah");
new Add1(n,t);

}

public void run()//接收
{
if(L1!=null&&L1.trim() != "")
{String n="[服务器：]";
new Add1(n,Socket1.L1);
}
}
}

Answer 1

测试过了你的代码，问题是Server端的socket的构造函数中是while(true)无限循环，导致后面的run方法打印接收到的响应代码无法执行。
把run方法中的代码挪到while循环中，如果收到客户端的代码后就打印到界面。
修正Server类的构造函数如下：

    socket() {
        try {
            s = new ServerSocket(9984);
            System.out.println("服务器开启：");
            while (true) {
                s1 = s.accept();
                System.out.println("received...");
                p1 = new PrintStream(s1.getOutputStream());
                in = new BufferedReader(new InputStreamReader(s1.getInputStream()));
                L2 = in.readLine();
                //收到
                System.out.println("L2:"+L2);
                if (L2 != null && L2.trim() != "") {
                    String n = "[客户：]";
                    new Add2(n, L2);
                }
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

测试过程：先启动Server端，然后启动Client，再Client输入发送信息后点击发送，然后转到Server端输入回复信息OK。