Socket s=ss.accept();
Client c=new Client(s);
new Thread(c).start();

------解决方案--------------------
把socket变量做为全局变量试试，这样收和发两个线程都能看到

------解决方案--------------------
使用TCP协议来进行服务器端与客户端的通信

服务器端：
package com.aikaibo.network;

import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class TcpServer
{
	public static void main(String[] args) throws Exception
	{
		ServerSocket ss = new ServerSocket(5000);
		//等待客服端的连接
		Socket socket = ss.accept();
		
		OutputStream os = socket.getOutputStream();
		
		os.write("hello".getBytes());
		
		InputStream is = socket.getInputStream();
		
		byte[] buffer = new byte[200];
		int length = is.read(buffer);
		
		System.out.println(new String(buffer, 0, length));
		
//		byte[] buffer = new byte[200];
//		
//		int length = 0;
//		
//		while(-1 != (length = is.read(buffer, 0, buffer.length)))
//		{
//			String str = new String(buffer, 0, length);
//			System.out.println(str);
//		}
		
		os.close();
		ss.close();
		socket.close();
	}
}


客户端:

package com.aikaibo.network;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;

public class TcpClient
{
	public static void main(String[] args) throws Exception, IOException
	{
		//与服务器端建立好连接
		Socket socket = new Socket("192.168.1.6", 5000);
		
		InputStream is = socket.getInputStream();
		
		byte[] buffer = new byte[200];
		
		int length = is.read(buffer);
		
		System.out.println(new String(buffer, 0, length));
//		int length = 0;
//		while(-1 != (length = is.read(buffer, 0, buffer.length)))
//		{
//			String str = new String(buffer, 0, length);
//			
//			System.out.println(str);
//		}
		
		OutputStream os = socket.getOutputStream();
		
	    os.write("wo".getBytes());
		is.close();
		os.close();
		socket.close();
	}
}