P2Pv1 Headers

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The flags define the type of P2P message that is being sent.

  • 0x0 Normal Message
  • 0x1 Nak
  • 0x2 Ack
  • 0x4 Waiting for a pending invite
  • 0x8 Notify a binary error
  • 0x10 File
  • 0x20 Msn Object: Display Picture or Custom Emoticon Data
  • 0x40 Close session
  • 0x80 Error at transport layer protocol
  • 0x100 Direct Handshake
  • 0x1000000 Define data for File transfer


The footer is 4 bytes long (DWORD) in big endian. It represents the Application Identifier (AppID)

  • 0x0 Negotiating session
  • 0x1 MsnObject: Display Picture or Custom Emoticon
  • 0x2 File transfer
  • 0xB CustomEmoticon (0d11)
  • 0xC Display Image (0d12)