Java socket EOFException

Question

I use RMI and socket to transfer files between a client set. The problem is when running the code below sometimes i get this exception in client side :

java.io.EOFException
at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2671)
at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:3146)
at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:858)
at java.io.ObjectInputStream.<init>(ObjectInputStream.java:354)
at javafxcyberwind.serverSocket.run(serverSocket.java:38)
at java.lang.Thread.run(Thread.java:748)

This is a sample of my code, the exceptions are in comment lines :

Client :

Server_MethodsPEER S = (Server_MethodsPEER) Naming.lookup("rmi://" + ip + ":" + port + "/" + email);
Server_Methods R = S.peer();
R.uploadToServer(fileName);
Socket s = new Socket(ip, R.getServerSocketPort());
File fres = new File(crep + fileName);
FileInputStream inf = new FileInputStream(fres);
ObjectOutputStream out = new ObjectOutputStream(s.getOutputStream());
byte buf[] = new byte[1024];
int nn;
while ((nn = inf.read(buf)) != -1) {
    out.write(buf, 0, nn);
}
out.close();
inf.close();
s.close();
fres.delete();

Server :

public class serverSocket implements Runnable {

private final ServerSocket socketserver;
private Socket socket;
private final String ff;
private final String rp;

public serverSocket(ServerSocket s, String file, String rep) {
    socketserver = s;
    ff = file;
    rp = rep;
}

@Override
public void run() {
    try {
        socket = socketserver.accept();
        ObjectInputStream in = new ObjectInputStream(socket.getInputStream());//EOFException here
        FileOutputStream out = new FileOutputStream(new File(rp + ff));
        byte buf[] = new byte[1024];
        int n;
        while ((n = in.read(buf)) != -1) {
            out.write(buf, 0, n);
        }
        in.close();
        out.close();
        socket.close();
        socketserver.close();
    } catch (IOException e) {
        System.err.println("socket err");
    }
}
}

//ServerIMPL
ServerSocket sv;

public void uploadToServer(String fileName) throws RemoteException {
    try {
        sv = new ServerSocket(0);
    } catch (IOException ex) {
        Logger.getLogger(Cloud_ServeurIMPL.class.getName()).log(Level.SEVERE, null, ex);
    }
    Thread t = new Thread(new serverSocket(sv, file, crep));
    t.start();

    Client3_MethodsPEER M = (Client3_MethodsPEER) Naming.lookup("rmi://" + ip + ":" + port + "/" + email);
    Client3_Methods U = M.peer();
    U.uploadToServer(fileName);
    Socket s = new Socket(ip, U.getServerSocketPort());
    File fres = new File(crep + fileName);
    FileInputStream inf = new FileInputStream(fres);
    ObjectOutputStream out = new ObjectOutputStream(s.getOutputStream());
    byte buf[] = new byte[1024];
    int nn;
    while ((nn = inf.read(buf)) != -1) {
        out.write(buf, 0, nn);
    }
    out.close();
    inf.close();
    s.close();
    fres.delete();
    U.operation();//FileNotFoundException here (use the received files as arguments)
}

Everything seems to be fine. Why is this happening and how to solve it ?

Answer 1

FileNotFoundException has two meanings:

1. On input, the file wasn't found, couldn't be opened due to permissions, etc.
2. On output, the target directory wasn't found, couldn't be written into due to permissions, etc.

For example if the filename you are sending contains a directory that doesn't exist at the server, you will get FileNotFoundException from new FileOutputStream.

There isn't enough (i.e. any) information in your question to say any more about that.

However:

• You don't need object streams for this, or even data input/output streams. You're only using the basic read() and write() methods, so you may as well just use the socket streams directly.

• You should use a larger buffer than 1024 bytes, say 8192 or a multiple thereof.

• You can send multiple files per connection via the technique given in my answer to this question.