Remote File Copy Homework

• Read about Sockets
• Example programs: MyClient.java; MyServer.java
• Write a program that does a remote copy of a file.
• Syntax is java jftp tofile fromfile where one of tofile or fromfile is of form filename@hostname.
• Use InputStream and OutputStream.
• There is an exchange of command messages after which the data flows.
• A command message is a one byte called the operation code, followed by an argument. The argument is one byte giving the number of bytes following, and then that many bytes of a Java String, converted to bytes.
• The protocol is decribed by the sequence of operation codes and the meaning of the argument:
  • First message: from server to client: operation code HELLO (0); argument is an arbitary HELLO-BANNER.
  • Second message: from client the server - the request. Either:
    • A READ-REQUEST (1); argument is the file name for the server to read and send to client.
    • A WRITE-REQUEST (2): argument is the file name for the server to write the data which the client will send.
  • Third message: from server to client: the response. Either:
    • An ACKNOWLEDGEMENT (4): argument is arbitrary.
    • An ERROR (5): arguement is an explanation, for instance "File Not Found"
  • If ACKNOWLEDGEMENT, then client and server exchange data bytes. If ERROR both close their sockets. The client exits; the server waits for the next connection.

  S->C: [0][10][jtfp ready]
  C->S: [1][8][test.txt]
  S->C: [4][2][OK]
  S->C: ... data bytes ...