BufferedReader在与TCP套接字一起使用时在字符串中提供更多的空字符

Question

My TCP Server is like this.

import java.net.*;
import java.io.*;
public class NetTCPServer {
public static void main(String[] args) throws Exception{

ServerSocket sock;
sock = new ServerSocket(1122);
if(sock == null)
    System.out.println("Server binding failed.");
System.out.println("Server is Ready ..");

do{
    System.out.println("Waiting for Next client.");
    Socket clientSocket = sock.accept();
    if(clientSocket!=null)
        System.out.println("Clinet accepted. "+sock.getInetAddress().getHostAddress());

    DataOutputStream out = new DataOutputStream(clientSocket.getOutputStream());
    //DataInputStream in = new DataInputStream(clientSocket.getInputStream());
    BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
    String name;
    String pass;
    String line;
    name = in.readLine();
    pass = in.readLine();
    for(int i=0;i<name.length();i++)
        System.out.print(name.charAt(i)+","); //see more null char are receiving here

        System.out.println("");
        System.out.println(name +"  "+ name.length()+"  \n" + pass+"  "+pass.length());
    }while(true);

}
}

And respective TCP Client is as follows.

import java.net.*;
import java.io.*;
public class NetTCPClient {

    public static void main(String[] args) throws Exception {
        InetAddress addr = InetAddress.getByName("localhost");

        Socket sock;
        sock = new Socket(addr,1122);
        if(sock == null)
            System.out.println("Server Connection failed.");
        System.out.println("Waiting for some data...");
        DataInputStream input = new DataInputStream(sock.getInputStream());
        DataOutputStream output = new DataOutputStream(sock.getOutputStream());
        String uname="ram";
        String pass="pass";
        output.writeChars(uname+"\n");// \n is appended just make to readline of server get line
        output.writeChars(pass+"\n");
        }

}

When i compiled both and the server is started and there after client is run, i get following output.

 Server is Ready .. Waiting for Next client. Clinet accepted. 0.0.0.0 ,r,,a,,m,, ram7 pass9 

The null character after each character receive is somewhat strange to me. To make me unable to compare the string with something stored in server. What is those null characters and where does they come from.

Answer 1

You write characters but read lines of bytes . That won't work. If you're going to write characters, you need to read characters with precisely the same encoding. If you're going to write bytes, you need to read bytes. Specify your protocol precisely at the byte level and follow the specification in both the client and the server.

See this question for more information.