File and Message transfer over sockets!

[rameshraj]

I am developing a chat application in JAVA and need to transfer the files from one user to another.I have successfully sent the messages from one user to another via the sockets.Now I want to transfer the file also using the same sockets.The problem is how the user side distinguishes whether s/he has received the message or the file.
Is there any other effective technique to do the same thing?
Also how can I use the drag and drop over the Swing GUI so that the user can simply drag the file to be sent over the socket on the GUI and then send the file

[danielstoner]

You have to implement your own "protocol" for doing this. you can also maintain connections open: one for commands and one for data. This is how FTP does it

[rameshraj]

public static void main(String[] args) throws Exception {
Thread serverthread = new Thread(new Runnable(){
public void run(){
ServerSocket ss = null;
try{

ss = new ServerSocket(44444);

Socket s = ss.accept();

OutputStream out = s.getOutputStream();
FileInputStream fin = new FileInputStream("Test.txt");
byte[] buf = new byte[1024];
int read;
while( (read=fin.read(buf)) != -1) {
out.write(buf, 0, read);

}..................................



I am using the above concept to read the file in a Stream and sending it to the OutputStream.
On the other side I am receiving similarly in a loop and saving it to a file:

String f2="E:/E-resources/java/Test.txt";
FileOutputStream fos = new FileOutputStream(new File(f2));

while(in.read(buf)!=-1)
{
fos.write(buf);
System.out.println("Writing to the file is\t"+buf[29]+".."+fos.getChannel().size());
}
.........................


Using this technique how can I distinguish the two(ordinary message and File Transfers).

[danielstoner]

As I said, you can use to channels, one for commands and one for data. Each command can have a unique ID generated on the server. The corresponding data will have the same ID. In order to do this you have to implements some protocol kind of protocol. Read a document like this RFC 959 (rfc959) - File Transfer Protocol to understand hot things are done usually.