Java套接字通过单流传输多个文件

Question

I have written a client-server file transfer program. I am trying to achieve the following workflow:

---

connect to server -> open stream -> authenticate -> mesage('Send File') -> message([file name]) -> message([file size]) -> send the file -> message('Send File') ... message('Disconnect')

---

The goal is to only connect and authenticate once and send multiple files over a single dataStream.

I have modified a stream copying method to make sure the copying does not copy too much data from the incoming and outgoing stream. This copy method is used on both the server and client for sending and receiving.

example sending a file from client to server:

Server: copy(dataInputStream, fileOutPutStream, length)

Client: copy(fileInputStream, dataOutputStream, length)

My question is do you see any potential problems with this approach?

static void copy(InputStream in, OutputStream out, long length) throws IOException {
    byte[] buf;
    if (length < 8192) {
        buf = new byte[(int) length];
    }
    buf = new byte[8192];
    int len = 0;
    long read = 0;
    while (length > read && (len = in.read(buf)) > -1) {
        read += len;
        out.write(buf, 0, len);
        if (length - read < 8192) {
            buf = new byte[(int) (length - read)];
        }
    }
}

Answer 1

while (length > read && (len = in.read(buf)) > -1) {
        read += len;
        out.write(buf, 0, len);
        if (length-read < 8192){
            buf = new byte[(int) (length-read)];
        }
    }

The easy way to do that is as follows:

while (length > read && (len = in.read(buf, 0, Math.min(buf.length, length-read))) > 0) {
        read += len;
        out.write(buf, 0, len);
        }
    }

E&OE

This way too, the buffer can be any size you like above zero without its size creeping into the code at several points.