code: func (b *Bzz) checkHandshake(hs interface{}) error {
  	rhs := hs.(*HandshakeMsg)
  	if rhs.NetworkID != b.NetworkID {
  		return fmt.Errorf("network id mismatch %d (!= %d)", rhs.NetworkID, b.NetworkID)
  	}
  	if rhs.Version != uint64(BzzSpec.Version) {
  		return fmt.Errorf("version mismatch %d (!= %d)", rhs.Version, BzzSpec.Version)
  	}
  	return nil
  }
docs: // Perform initiates the handshake and validates the remote handshake message