客户端应该这样写:
Socket socket=new Socket("localhost",6666);
File file=new File("c:/zwp/test.txt");
FileInputStream filein=new FileInputStream(file);
OutputStream out=socket.getOutputStream();
byte[] buf = new byte[4096];
int bytes = 0;
while((bytes = filein.read(buf)) != -1)
    out.write(buf, 0, bytes);
out.flush();
out.close();
filein.close();