1.) How and where are transaction fees calculated exactly. Had this post in the forum. https://forum.cardano.org/t/variable-fees-on-cardano/95517?u=heptasean The theoretical maximum transaction fee should be 0.876 ADA, but Daedalus automatically used 1.19 ADA (although he was probably far from the maximum transaction size of 16 KiB). Where do I find that bug? Daedalus source? Or does it delegate to cardano-node and there is something off there? 2.) cardano-cli uses a socket to communicate with cardano-node. What protocol is spoken on that socket? How can I write my own client in a language more accessible (to me)?

Fee calculation is tricky as it is like chicken and egg situation, as it is based from the size of tax but a tax must include the fee. That is why Daedalus just overestimated but it was very long ago iirc.

The node2client protocol I created some diagram last year or beforefor general public to understand how it works. https://github.com/ilap/ShelleyStuffs#network-communications

1) The calculation of fees is described here and is essentially unchanged: https://iohk.io/en/blog/posts/2017/10/19/how-cardanos-transaction-fees-work/ You also need to add the mechanism for calculating the ada to be added to the token bundle, if any: https://cardano-ledger.readthedocs.io/en/latest/explanations/min-utxo-alonzo.html 2) Depending on the OS used cardano-node and cardano-cli communicate via unix sockets or via a named pipe. The details of the communication protocol are described here: https://docs.cardano.org/explore-cardano/cardano-network/networking-protocol You should also understand the serialization format used, CBOR.