| Transmitting / receiving hex values [message #882513] |
Wed, 06 June 2012 15:56  |
 Tony Verrall
Messages: 3
Registered: June 2012 |
Junior Member |
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I am new to the forums, and may have posted this to the wrong one - please help a newbie. 
As part of project to develop Android App, I need to be able to connect from the app to a set location, which has a small microprocessor based(unchangable) LAN interface, which will accept set commands in hex. The response is given in hex.
Using a sample socket program, which I have tried to modify (see code below), I can see (using wireshark) that the transmitted string is in ASCII, not hex, so I am sending 38 bytes, and not the 18 with the 0x prefix.
I have tried using a LONG, but the value I am trying to send is too large (see String process = '0x.....' midway through the code), and I get 'The literal 0x.... of type int is out of range.
I would appreciate someone pointing me in the right direction.
Thanks
// package bdn;
/* The java.net package contains the basics needed for network operations. */
import java.net.*;
/* The java.io package contains the basics needed for IO operations. */
import java.io.*;
/** The SocketClient class is a simple example of a TCP/IP Socket Client.
* For a detailed explanation of the classes in this project see
* bdn.borland.com/article/0,1410,31995,00.html
*/
public class SocketClient {
public static void main(String[] args) {
/** Define a host server */
String host = "192.168.1.199";
/** Define a port */
int port = 3376;
int i = 0;
StringBuffer instr = new StringBuffer();
// String TimeStamp;
System.out.println("SocketClient initialized to " + host + ", port " + port );
try {
/** Obtain an address object of the server */
InetAddress address = InetAddress.getByName(host);
/** Establish a socket connection */
Socket connection = new Socket(address, port);
/** Instantiate a BufferedOutputStream object */
BufferedOutputStream bos = new BufferedOutputStream(connection.
getOutputStream());
/** Instantiate an OutputStreamWriter object with the optional character
* encoding.
*/
OutputStreamWriter osw = new OutputStreamWriter(bos, "US-ASCII");
// TimeStamp = new java.util.Date().toString();
String process = "0x308101000c00234C51050000000099670007";
System.out.println("Data to be sent is " + process) ;
/** Write across the socket connection and flush the buffer */
osw.write(process);
osw.flush();
System.out.println("Data sent is " + process) ;
/** Instantiate a BufferedInputStream object for reading
* incoming socket streams.
*/
BufferedInputStream bis = new BufferedInputStream(connection.
getInputStream());
/**Instantiate an InputStreamReader with the optional
* character encoding.
*/
InputStreamReader isr = new InputStreamReader(bis, "US-ASCII");
/**Read the socket's InputStream and append to a StringBuffer */
int c;
for (i = 0; i <= 18; i++ ) {
c = isr.read() ;
instr.append((char) c);
System.out.println("character " + i + " value " + c);
}
/** Close the socket connection. */
connection.close();
System.out.println(instr);
}
catch (IOException f) {
System.out.println("IOException: " + f);
}
catch (Exception g) {
System.out.println("Exception: " + g);
}
}
}
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