C服务器到Java客户端套接字读取以短值传递

Question

I am having difficulty just passing a short value from a C server. What I receive on the other end is 'junk' it looks like, and I can't seem to convert it into something useful.

Factors I think are influencing it

1. 2s complement
2. Potential ASCII or UTF-8 enconding

Starting with C code:

        // Read 10 bit value into short
        unsigned short ret = decideActionCall(buffer);  
        unsigned char lsb = (unsigned char) ret;
        unsigned char msb = (unsigned char) (ret >> 8);

        printf("msb,lsb = %02x,%02x\n",msb, lsb);

        /**
        char retString [4];
        retString[0] = msb;
        retString[1] = lsb;
        retString[2] = '\n';
        retString[3] = '\0';
        */

        unsigned short retString1[1];
        retString1[0] = ret;

        printf("msb,lsb = %d,%d\n",retString[0],retString[1]);

        printf("String to send: <%s>\n",retString1);
        //if (write(newsockfd, retString, 3) < 0) {
        //  error("Error sending response to the server");
        //}
        if (write(newsockfd, &retString1, 2) < 0) {
          error("Error sending response to the server");
        }
        if (write(newsockfd, "\r",1) < 0) {
          error("Error sending response to the server");
        }

And the terminal output is

START-----------------------------

0 0
136 0x88
ADC3 = 136

END-----------------------------
decideActionCall() ret value: 136
msb,lsb = 00,88
msb,lsb = 0,136
String to send: <�>

So the return for 'ret' is a value between 0 and 1023 (0x3FF). These 10 bits need to be transferred from C server to client. I have tried two implementations where I send them as 8 bit chars (retString) or one 16 bit short (retString1). Sizeof(char) == 1 , and sizeof(short) == 2 .

Java Code (with various attempts to parse it):

BufferedReader bufIn = new BufferedReader(new InputStreamReader(in));
String response = bufIn.readLine();

char [] hello = response.toCharArray();
for (char a : hello) {
    short shortA = (short) (a & 0x3FF);
    System.out.println(a + " = " + (int)a + " = " + shortA);


    //System.out.println((int)a);
    //System.out.println(Integer.valueOf(a+"",10));
    }

byte test[] = response.getBytes("UTF-8");

StringBuilder sb = new StringBuilder();
for (byte b : test) {
     sb.append(String.format("%02X ", b));
}
System.out.println(sb.toString());

byte b05 = 0x00;
byte b06 = 0x00; // MSB, positive as < 0x80

int i = 0;
for (byte a : test) {
    //System.out.println(short1);
    System.out.println("byte: " + a);
    //System.out.println(Integer.valueOf(a+"",10));

    if (i == 0 ) {
        b05 = a;
    } else {
        b06 = a;
    }

    i++;
    }

    System.out.println("i = "  + i);

    byte[] byteTabDay = new byte[2];
    byteTabDay[0] = b05;
    byteTabDay[1] = b06;

    BigInteger temp = new BigInteger(test);
    System.out.println(temp);
    System.out.println(temp.intValue());
    System.out.println(temp.shortValue() + 65536);

    BigInteger temp2 = new BigInteger(byteTabDay);
    System.out.println(temp2);
    System.out.println(temp2.shortValue() + 65536);

Java sample output (android logcat):

I/System.out﹕ response: ���
I/System.out﹕ here: � 65533
I/System.out﹕ ascii: 65485 65581
I/System.out﹕  � = 65533 = 1021
I/System.out﹕ �� = 0 = 0
I/System.out﹕ EF BF BD 00
I/System.out﹕ byte: -17
I/System.out﹕ byte: -65
I/System.out﹕ byte: -67
I/System.out﹕ byte: 0
I/System.out﹕ i = 4
I/System.out﹕ -272646912
I/System.out﹕ -272646912
I/System.out﹕ 48384
I/System.out﹕ -4352
I/System.out﹕ 61184

Questions:

1. How should I properly read the socket?
2. How do I properly read the 10 bits? (I've tried masking the char with 0x3FF)
3. Is two's complement potentially causing problems?

Thank you,

Answer 1

1. You're receiving binary, so you shouldn't be using a Reader at all. You should be using DataInputStream.readShort().
2. That is correct.
3. No.