记tcp网络编程中遇到的readline()方法

客户端

public static void main(String[] args) throws UnknownHostException, IOException {
		// TODO Auto-generated method stub
		Socket socket = new Socket("192.168.43.195", 12344);
		
		BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
		System.out.println(br.readLine());
		socket.close();
	}

服务端

public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		
		ServerSocket server = new ServerSocket(12344);
		Socket socket  = server.accept();
		
		BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
		String line = "hello";
		bw.write(line);
	}

代码很简单，能够看到从服务端发出的hello要在客户端输出，可是在运行后并无达到预期的效果。

除非把server端的输出流关闭才能够在client端输出，在输出流关闭后bw.close()会返回一个null。readline()是一个阻塞函数，在没有数据读的时候会一直卡在那里等待/r/n的出现

分析程序在服务端写入的hello以后客户端则读取，这里选用bufferedreader是由于他里面有一个能够读取整行的方法。调用br.readline()方法以后返回的是string，可是在行的末尾没有/r和/n,readline方法也就没办法中止，一直卡在这里。知道问题出在这里想了一下解决办法，在输入的字符串的末尾加/r/n可是我没有成功，改善的代码以下：

客户端：

public static void main(String[] args) throws UnknownHostException, IOException {
		// TODO Auto-generated method stub
		Socket socket = new Socket("192.168.43.195", 12344);
		
		BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
		PrintStream ps = new PrintStream(socket.getOutputStream());
		
		System.out.println(br.readLine());
		socket.close();
	}

服务端：

public static void main(String[] args) throws IOException {
		
		ServerSocket server = new ServerSocket(12344);
		Socket socket  = server.accept();
		
		BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
		PrintStream ps = new PrintStream(socket.getOutputStream());
		ps.println("hello");
	}

能够看到在ps调用的println方法后会自动换行，此时跳到client端当读到hello的末尾会识别到换行符，就能够打印输出了。