I heard recently that its possible to write plain text messages in the blockchain.
How can one do that? Can someone explain me how can I do that using bitcoin-qt?
User level functionality to do this does not yet exist in Bitcoin-Qt (and perhaps never will).
You would need to create your own raw transactions with the message already encoded. Then you can use Bitcoin-Qt to broadcast the raw transaction if you like.
And how can I read my message and others? using bitcoin-qt
User level functionality to do this does not yet exist in Bitcoin-Qt (and perhaps never will).
From the console in the debug window you could issue the command getrawtransaction if you know the transaction ID.
or blockchain.info?
View the transaction with the block explorer. Make sure you click the "show scripts & coinbase" link.