java TCP 代码

server/client模式代码不难，主要用到java的socket类和serversocket类，但是在运行过程中遇到问题。

现象：文中代码注释部分用的BufferedReader.readline()函数，这句代码无法执行。我调试很久，发现由于以下原因

原因：

（1）BufferedReader的readLine方法只有在遇到流结尾或者流关闭了才会返回null

（2）对于读取文件流，当读到文件的结尾时，就是到了流的结尾

（3）但对于socket，不能认为把某次写入到流中的数据读取完了就算流结尾了，但是socket流还存在，还可以继续往里面写入数据然后再读取。所以用BufferedReader封装socket的输入流，调用BufferedReader的readLine方法是不会返回null的

改正方法是

byte[] buf = new byte[1024];
InputStream in = socket.getInputStream();

int i=0;
while((i=in.read(buf))!=-1){
String s = new String(buf);
System.out.println(s);
}
System.out.println("接受完了！");

以上代码参考   http://blog.youkuaiyun.com/dyc9891009/article/details/8141200

我的代码如下：

servercode:

package test;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;

public class SocketServer {

	public static void main(String[] args) throws IOException {
		// TODO server
		FileWriter fw = new FileWriter(new File("/resultserver.txt"));
		BufferedWriter bw= new BufferedWriter(fw);
		bw.write("server\n");
		ServerSocket ss = new ServerSocket();
		//ss.setReuseAddress(true);
		ss.bind(new InetSocketAddress(40000));
		String line = null;
		String receive = "";
		Socket socket = null;
		socket = ss.accept();
		socket.setKeepAlive(true);
		
		String[] temp = {"我是服务端，接收到了你的消息，谢谢！","bye"};
		PrintWriter os = new PrintWriter(socket.getOutputStream());
//		BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
//		String str = "";
//		int i=0;
//		System.out.println(1111111);
		os.println("我是服务端，接收到了你的消息，谢谢！");
		os.println("bye");
		os.flush();
		byte[] buf = new byte[2048];  
		InputStream in = socket.getInputStream();  
		int i = in.read(buf);  
		String request = new String(buf,0,i);  
		System.out.println(request);  
//		while(!"bye".equals(str= br.readLine())){
//			os.println(temp[i++]);
//			os.flush();
//			System.out.println(str);
//		}
		System.out.println(2222222);
		System.out.println(receive);
		
		bw.write("服务端收到 "+receive+"\n");
		os.close();
		//br.close();
		
		socket.close();
		ss.close();
		bw.write("server end\n");
		bw.flush();
	}
}

clientcode:

package fdsa;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.FilterWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.UnknownHostException;

public class SocketClient {

	public static void main(String[] args) throws InterruptedException, UnknownHostException, IOException {
		// TODO client
		FileWriter fw = null;
		fw = new FileWriter(new File("/resultclient.txt"));
		BufferedWriter bw= new BufferedWriter(fw);
		bw.write("client\n");
		Socket socket = new Socket();
		socket.connect(new InetSocketAddress(InetAddress.getByName("127.0.0.1"),40000));
		String receive = "";
		
		PrintWriter os = null;
		os = new PrintWriter(socket.getOutputStream());
//		BufferedReader br = null;
//		br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
//		String[] temp = {"我是客户端","bye"};
//		String str = "";
//		int i=0;
//		System.out.println(1111111);
		os.println("我是客户端");
		os.println("bye");
		os.flush();
		byte[] buf = new byte[2048];  
		InputStream in = socket.getInputStream();  
		int i = in.read(buf);  
		String request = new String(buf,0,i);  
		System.out.println(request);  
//		while(!"bye".equals(str= br.readLine())){
//			os.println(temp[i++]);
//			os.flush();
//			System.out.println(str);
//		}
		System.out.println(2222222);
		bw.write("客户端收到"+receive);
		bw.write("client end\n");
		bw.flush();
		
		os.close();
		//br.close();
		socket.close();
		}
}