In Curl lib 7.19.4, tftp_tx() is not handling the case for TFTP_EVENT_OACK. This case should be added in tftp_tx(). In tftp_rx(), this case is already handled.
In RFC 2348,it is given as "If the server is willing to accept the blocksize option, it sends an Option Acknowledgment (OACK) to the client."
I was not able to upload files, as we are not handling this scenario.