starting alphad what is the correct rpcconnectport following the instructions in the alpha-README.md file on GitHub
in step number 2, to start alphad it is suggested to do:

./alphad -rpcuser=$RPC_USER -rpcpassword=$RPC_PASS -testnet -rpcconnect=127.0.0.1 -rpcconnectport=18332 -tracksidechain=all -txindex -blindtrust=true -daemon


my question is about the rpcconnectport=18332
why 18332 instead of 4241?  like in step 5
Because in order to validate sidechain transfers, alphad needs to connect to a testnet bitcoind. The rpcconnect-like flags passed to it are information about how it can do that, so you need to use the running bitcoind's port.