通过TCP / IP读取数据包时出错

Question

I'm making a development for connecting one client to a specific tipe of server over TCP/IP. I am creating a code that to send bytes over TCP/IP and receive bytes.

The problem is when I receive the packets in certain point it breaks.

String input;
Traductor traductor = new Traductor();
PrintWriter writer = new PrintWriter(this.socket.getOutputStream(), true);
// Write a message to server       
byte[] theBytesInmediate = new byte[]{0x11, 0x00, 0x14, 0x50, 0x00, 0x01,  0x04, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0x7F, (byte) 0x0A, 0x02, (byte)0x2A, 0x00, 0x02, 0x02, 0x31, 0x00};
DataOutputStream salida = new DataOutputStream(this.socket.getOutputStream());
salida.write(theBytesInmediate);
System.out.println("Packet sent"); 
InputStream input2 = socket.getInputStream();

String tmp ="";
while(true){
     DataInputStream entrada = new 
     DataInputStream(this.socket.getInputStream());
     System.out.println("bytes: " + entrada.readByte());
     try{
        tmp =tmp +  entrada.readUTF();
        System.out.println("readUTF: " + tmp);
     }catch(IOException e){
                System.out.println(e);
     }      
     System.out.println("read: " + entrada.read());
     System.out.println("readChar: " + entrada.readChar());
     System.out.println("readLong: " + entrada.readLong());
}

Here is my output in console:

One problem is when I try to get all the packet if you see on the image it breaks, and only get part.

The second problem if I delete this lines:

System.out.println("read: " + entrada.read());
System.out.println("readChar: " + entrada.readChar());
System.out.println("readLong: " + entrada.readLong());

The getting packet stops in first P blank blank blank, part of packet.

I test with BufferedReader reader = new BufferedReader(new InputStreamReader(input2)); but the reading packet is incorrect.

And I know that the packets are incorrect because I am checking it with Wireshark.

The important part of packet I need is that tells 13001 there is for mi id.

Thanks a lot to all.

Update:

With my new code thanks to EJP, is working now, but one line is missin at last (I think).

PrintWriter writer = new PrintWriter(this.socket.getOutputStream(), true);  
byte[] theBytesInmediate = new byte[]{0x11, 0x00, 0x14, 0x50, 0x00, 0x01,  0x04, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0x7F, (byte) 0x0A, 0x02, (byte)0x2A, 0x00, 0x02, 0x02, 0x31, 0x00};
DataOutputStream salida = new DataOutputStream(this.socket.getOutputStream());
String str = new String(theBytesInmediate, StandardCharsets.UTF_8);

writer.println(str);
//writer.flush();
System.out.println("Packet sent"); 
InputStream input2 = this.socket.getInputStream();

BufferedReader reader = new BufferedReader(new InputStreamReader(input2));
String tmp ="";
while(true)
{
   System.out.println("read: " + reader.readLine().toString());
   System.out.println("read: " +reader.read());         
}

Output:

If you see in the output is missin the large paquet where the ip from the last id is. Is not a large problem. But if I need to end the while, is needed.

Thanks a lot to all.

Answer 1

You are reading with readUTF() but you are not writing with writeUTF() . Have a look at the Javadoc. There is no chance that readUTF() can read data written with write() .

You also need to decide as between Reader and Writer on the one hand and input/output streams on the other hand. Don't mix them.

Answer 2

I will point out some problems: DataOutputStream requires flush() to be certain the output is actually written. The data you write does not seem to agree with the read methods and the results. In UTF P is 0x50. -553882341120 is FF FF FF 7F 0A 0A 31 00. The proper way to go is that the write methods agree with the read methods, for example readLong should be matched with writeLong.