java如何接收和发送ASCII数据

public static String getString(ByteBuffer buffer) {
		Charset charset = null;
		CharsetDecoder decoder = null;
		CharBuffer charBuffer = null;
		try {
				charset = Charset.forName("GBK");
				decoder = charset.newDecoder();	
				charBuffer = decoder.decode(buffer.asReadOnlyBuffer());	
				return charBuffer.toString();
		} catch (Exception ex) {
			//ex.printStackTrace();
			return "";
		}
	}

public int SendTcpData(String strData){
    byte[] szCmd= new byte[1024];
    int iWriteRet = 0;
    byte bydata[];
    try {
        bydata = strData.getBytes("GBK");
        System.arraycopy(bydata, 0, szCmd, 0, bydata.length);
        int len = bydata.length;
        ByteBuffer cacheBuffer = ByteBuffer.allocate(len);
        cacheBuffer.put(szCmd,0,len);
        cacheBuffer.flip();
        int iWriteRet = sock.write(cacheBuffer);
        if(iWriteRet<0){
        }
    } catch (Exception e) {
	    //e.printStackTrace();
    }
    return iWriteRet;
}

import java.util.Scanner; 
public class Test { 
	public static void main(String[] args)throws Exception{ 
		Scanner in = new Scanner(System.in); 
		String b = in.next(); 
		for( int i=0;i< b.length();i++){ 
			System.out.println( b.charAt(i)+" "+(byte) b.charAt(i)); 
		} 
	} 
} 

package demo;
public class TestASCII01 {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		for(int i=0;i<255;i++){
			char a = (char) i;
			System.out.println(a+" "+i);
		}
	}
}