Socket中的流读取结束判断

Question

今天写了一个程序，本想没什么问题，可是运行起来以后却发现是死锁。死锁发生的地方我已经用注释标明，希望各位大侠发表看法。Server端代码：import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;public class TcpServer {
public static void main(String[] args) {
ServerSocket server = null;
Socket socket = null;
BufferedReader reader = null;
PrintWriter writer = null; try {
// bind port 2222 and read message from client
server = new ServerSocket(2222);
socket = server.accept();
reader = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
String str = null;
while ((str = reader.readLine()) != null) { // 好像在这里readLine()没有读到值就会一直阻塞，导致客户端无法继续运行
str = reader.readLine();
System.out.println(str);
} // send message to client
writer = new PrintWriter(new OutputStreamWriter(
socket.getOutputStream()), true);
writer.println("Thanks");
writer.flush();
writer.println("bye");
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (writer != null) {
writer.close();
writer = null;
}
if (reader != null) {
reader.close();
reader = null;
}
if (socket != null) {
socket.close();
socket = null;
}
if (server != null) {
server.close();
server = null;
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Client端代码：import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;public class TcpClient {
public static void main(String[] args) {
Socket socket = null;
PrintWriter writer = null;
BufferedReader reader = null;

try {
// connect server and send message
socket = new Socket("127.0.0.1", 2222);
writer = new PrintWriter(new OutputStreamWriter(
socket.getOutputStream()), true);
writer.println("Hello");
writer.flush();
writer.println("world" + File.separatorChar);
writer.flush();

// receive message from server
String str = null;
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
while((str = reader.readLine()) != null){
str = reader.readLine();
System.out.println(str);
}
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if(reader != null){
reader.close();
reader = null;
}
if (writer != null) {
writer.close();
writer = null;
}
if (socket != null) {
socket.close();
socket = null;
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}

Answer 1

package test.io;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;public class TcpServer {
    public static void main(String[] args) {
        ServerSocket server = null;
        Socket socket = null;
        BufferedReader reader = null;
        PrintWriter writer = null;        try {
            // bind port 2222 and read message from client
            server = new ServerSocket(2222);
            socket = server.accept();
            reader = new BufferedReader(new InputStreamReader(
                    socket.getInputStream()));
            String str = null;
            while ((str = reader.readLine()) != null) { // 好像在这里readLine()没有读到值就会一直阻塞，导致客户端无法继续运行
                System.out.println(str);
            }            // send message to client
            writer = new PrintWriter(new OutputStreamWriter(
                    socket.getOutputStream()), true);
            writer.println("Thanks");
            writer.flush();
            writer.println("bye");
            socket.shutdownOutput();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (writer != null) {
                    writer.close();
                    writer = null;
                }
                if (reader != null) {
                    reader.close();
                    reader = null;
                }
                if (socket != null) {
                    socket.close();
                    socket = null;
                }
                if (server != null) {
                    server.close();
                    server = null;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
package test.io;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;public class TcpClient {
    public static void main(String[] args) {
        Socket socket = null;
        PrintWriter writer = null;
        BufferedReader reader = null;
        
        try {
            // connect server and send message
            socket = new Socket("127.0.0.1", 2222);
            writer = new PrintWriter(new OutputStreamWriter(
                    socket.getOutputStream()), true);
            writer.println("Hello");
            writer.flush();
            writer.println("world");
            writer.flush();
            socket.shutdownOutput();
            
            // receive message from server
            String str = null;
            reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            while((str = reader.readLine()) != null){
                System.out.println(str);
            }
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if(reader != null){
                    reader.close();
                    reader = null;
                }
                if (writer != null) {
                    writer.close();
                    writer = null;
                }
                if (socket != null) {
                    socket.close();
                    socket = null;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

Answer 2

            while((str = reader.readLine()) != null){
                //str = reader.readLine();
                System.out.println(str);
            }