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  1. #1
    Bluefox815 is offline Member
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    Default [SOLVED] Byte value comes out negative

    I'm having some trouble with getting an IP address to come out in all positive numbers. Here is the code I'm using:

    Java Code:
    // host and port are given by the user
    Socket socket = new Socket(host, port);
    byte[] ipAddr = socket.getInetAddress().getAddress();
    String hostAddr = ipAddr[0] + "." + ipAddr[1] + "." + ipAddr[2] + "." + ipAddr[3];
    String hostDir = "data/" + hostAddr;

    The socket object made a connection without a problem. But other parts of the program are failing because if any of the 4 pieces of the IP addresses (also known as "octets") are over 127, then the number comes out negative because apparently a 'byte' in Java is signed.

    I have tried converting the number to an 'int' value in an attempt to make it seem unsigned, but it still came out negative.

    Java Code:
    // these didn't work
    Byte.valueOf(ipAddr[0]).intValue();
    Integer.valueOf(ipAddr[0]);

    Any help on converting a negative byte to the corresponding positive number is appreciated.

    EDIT: Convert an UNSIGNED byte to a JAVA integer - Real's Java How-to
    Last edited by Bluefox815; 07-03-2010 at 01:59 AM.

  2. #2
    Norm's Avatar
    Norm is offline Moderator
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    Default

    The trick is to AND the int that came from the byte with 0xFF to strip off all the sign bits.
    Try this:
    Integer.valueOf(ipAddr[0] & 0xFF);

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