How can I send or store an arbitrary text message to another EOS account?

Question

I wan't to be able to send a text string to another EOS account. How can this be done? Are there any mobile wallets that support this?

Answer 1

Yes, you can send arbitrary text messages to any account using the require_recipient() function. This function will introduce an inline action that communicates the parameters passed to the action to the desired recipient.

Example contract:

send_messages.cpp

#include <eosiolib/eosio.hpp>
#include <string>

using eosio::contract;
using std::string;

class send_messages : contract {
    public:
        send_messages(account_name account) : contract(account) {};

        void send(account_name account, string message) {
            require_recipient(account);
        }
};

EOSIO_ABI(send_messages, (send));

Afterwards, pushing an action to the contract as follows:

$ cleos push action <account-name> send '["<recipient>", "message"]' -p <acount-name>

would send the string "message" to the <recipient> in the form of an action.

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In regards to wallet support for this, you only need a software that allows you to push actions to your contract, which would be enough as long as you publish your contract on the blockchain first.

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what is the max character limit? and what is the cost of sending 1K, 10K, and 100KB text message.

There's not really a hard max character limit, as you can send as many strings of max_size() as you want. However, to process larger strings, you need more CPU and NET staked, but these resources are a bit impractical to approximate right now, especially as EOS renting systems would make this cheaper.

Naive calculation

However, if you want a back of the envelope calculations, perhaps you'd need to have staked about 0.01 EOS / 10,000 bytes message / day at current rates.

Explanation:

NET

For NET you'd need approximately as many bytes the message has + ~100bytes (e.g. you'd need 10,100 bytes to send a 10,000 bytes message.) According to eosrp.io, the price right now is 0.00050833 EOS/KiB/Day, so perhaps you'd look at 0.005 EOS / 10,000 bytes message / day for NET

CPU

This depends on the BP, the load, etc, and it's highly volatile, but I just tried to make such a transaction on Jungle testnet, and I got 2,000us. At current price of 0.00269295 EOS/ms/Day, that'd be ~0.005 EOS / 10,000 bytes message / day for CPU