TFTP Server
Written by Harpa Guðrún Hreinsdóttir and Sóley Ásgeirsdóttir

To run the server, simply pass the desired port number and data folder to the program as arguments (in that order).
Ctrl+c stops the server from running. Otherwise it will keep listening on the port and send files as requested.

We have struct for request, data, ack and error. 
We have the following methods outside the main. 

readRequest: reads message and puts it into the request struct. 

readData: reads message and puts it into the data struct. 

readAck: reads message and puts it into the ack struct. 

combDir: This method combines the file and directory.

fileExists: this method checks if a filepath exists or not.

serror: sends an error message

sendDataPacket: sends a data packet.