How to send to the socket EOF flag? Only socket.close() works fine :)

Question

I send a binary file from server socket to client socket. And I have some problem with client (but actually with server :) ).
That is my server code which sends a file:
OutputStream os = null;
FileInputStream fis = null;
try{
    fis = new FileInputStream( "some-file.png" );
} catch ( FileNotFoundException e1 ) {}
try {
    os = socket.getOutputStream();
    int c = -1;
    while( ( c = fis.read() ) != -1 ) {
        os.write( c );
    os.flush();
//    os.close();
} catch ( IOException e2 ) {}And that is client which receives a file:
try {
    int sChunk = 8192;
    InputStream is = socket.getInputStream();
    FileOutputStream out = new FileOutputStream( "file.png" );
    byte[] buffer = new byte[ sChunk ];
    int length;
    while ( ( length = is.read( buffer, 0, sChunk ) ) > -1 )
        out.write( buffer, 0, length );
    out.close();
} catch ( IOException e ) {
}A client's while never continues cause I don't know how to send EOF from server.
If I do: "os.close();" at the end of server sending - it works... But.. It closes my socket! But I want to work with socket after that :)
How to send correct EOF flag from server? I think it's the root of all problems here..
Edited by: JavaProger on Mar 22, 2009 4:43 PM

Answer 1

os = socket.getOutputStream();
int c = -1;
while( ( c = fis.read() ) != -1 ) {
os.write( c );
}That's about as inefficient as it could be. Try this:
int count;
byte[] buffer = new byte[8192];
while ((count = fis.read(buffer)) > 0)
os.write(buffer, 0, count);
os.close();
Hmm, you're doing that in the client, why not in the server?
} catch ( IOException e2 ) {}Never ignore an exception. In this case you should close the socket.
} catch ( IOException e ) {See above.
A client's while never continues cause I don't know how to send EOF from server.You can't send an EOF from the server. You can cause an EOS (end of stream on the socket) at the reader, by closing the socket, or shutting down its output, but then you can't send anything else on the socket. You have two choices:
(a) use a connection per file. If the files are large the overhead is minimal.
(b) use an application protocol to tell the reader when the file is complete. Typically this takes the form of sending the file length as a long first, and taking care to read exactly that many bytes when reading, which takes a bit of care, especially on the last buffer. Another way is to send the length ahead of each buffer, sending zero after the last buffer. You can do all this with the methods of DataInputStream and DataOutputStream.