UDPFileTransfer

Send or receive files over UDP. Start the receiver first, then the sender.

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Usage:

• Mode: send, recv
• Filename
• Sender address (IP:Port)
• Recvr address (IP:Port)

Example:

python file_transfer.py send somefile01.txt 192.168.8.111:9510 192.168.8.103:9510

python file_transfer.py recv somefile01.txt 192.168.8.111:9510 192.168.8.103:9510

NOTE:

Socket timeout in both modes is set to 20 seconds by default. If you're sending a big file and the program might take longer than 10 seconds to read and process the data, consider increasing the value of sock_timeout in the script, to avoid reaching socket timeout.

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Program flow:

• Receiver starts and waits for SendReq.
• Sender starts, reads and process file data, and sends SendReq containing chunk count, file checksum and other other data.
• Receiver receives SendReq, stores the data and sends SendAccept.
• Sender receives SendAccept and sends FilePkt containing chunk data.
• Receiver receives FilePkt and sends FilePktAck containing chunk checksum. Sender will use this checksum to confirm that the correct chunk data was received by receiver.
• Previous two steps repeat until receiver has received last FilePkt.
• Upon receiving last FilePkt, receiver sends EOFPkt, writes data to file and terminates. EOFPkt contains file data checksum.
• Sender receives EOFPkt, confirms whether the file data checksum matches, and terminates.

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Message Format:

• Byte 0: Magic Number
• Byte 1: MsgType: SendReq, SendAccept, FilePkt, FilePktAck, EOFPkt
• Byte 2-5: Data Size
• Byte 6-n: Data (depends on MsgType)
  • SendReq
    • Byte 6-9: Total number of FilePkts
    • Byte 10: Address Data Offset
    • Byte 11: Address Data Size
    • Byte 12: FileDataChecksum Offset
    • Byte 13: FileDataChecksum Size
    • Byte 14-17: DataBlob Size
    • Byte 18-n: Data Blob.
      • NOTE: Offsets and sizes will help you determine how to read data from blob. Offsets are relative to starting position of data blob.
      • General layout: Address Data | FileDataChecksum
  • SendAccept
    • Byte 6: Address Data Size
    • Byte 7-n: Adress Data
  • FilePkt
    • Byte 6-9: ChunkNumber
    • Byte 10-13: ChunkSize
    • Byte 14-n: ChunkData
  • FilePktAck
    • Byte 6-9: ChunkNumber
    • Byte 10-13: ChunkDataChecksumSize
    • Byte 14-n: ChunkDataChecksum (MD5)
  • EOFPkt
    • Byte 6-9: Total FilePkts received
    • Byte 10: FileDataChecksumSize
    • Byte 11-n: FileDataChecksum (MD5, full file data)