How to use `polkadot-api` to send multiple transactions simultaneously?

Question

experimental environment: m1 pro macbook

when I want send more transactions. the code will report this to me:

 RPC-CORE: submitAndWatchExtrinsic(extrinsic: Extrinsic): ExtrinsicStatus:: 1014: Priority is too low: (12562 vs 12562): The transaction has too low priority to replace another transaction already in the pool.
2022-04-09 23:44:45             DRR: 1014: Priority is too low: (12562 vs 12562): The transaction has too low priority to replace another transaction already in the pool.
2022-04-09 23:44:45        RPC-CORE: submitAndWatchExtrinsic(extrinsic: Extrinsic): ExtrinsicStatus:: 1014: Priority is too low: (12562 vs 12562): The transaction has too low priority to replace another transaction already in the pool.

My solution to this is to start multiple dockers and repeat the script. but I found that I could not connect over the IP(like 192.168.xxx.xxx) of the LAN. Parallel chains can only be connected through 127.0.0.1.(Even localhost is not supported). this is my parachain start command.

./target/release/dorafactory-node \
--alice \
--collator \
--force-authoring \
--chain dora-roc-testnet.json \
--base-path /tmp/parachain/alice --log=info,xcm=trace,xcm-executor=trace \
--port 40334 \
--ws-port 8845 --ws-external --rpc-external --rpc-methods=unsafe --prometheus-port 9777 --prometheus-external \
-- \
--execution wasm \
--chain rococo-local-cfde.json \
--port 30344 \
--ws-port 9978

and this my hosts:

##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting.  Do not change this entry.
##
127.0.0.1   localhost

this is my LAN ip:

this is my js-script error report:

this is my WEB_SOCKET on my js-script:

const { ApiPromise, WsProvider, Keyring } = require('@polkadot/api');

const WEB_SOCKET = 'ws://192.168.1.4:8845';
const wsProvider = new WsProvider(WEB_SOCKET);

Answer 1

The polkadot-js api cookbook has an example of this, which uses the system.accountNextIndex rpc.

Overall you have a couple of options -

1. Pass the nonce in as -1, which will use the above RPC to check against the pool (the docs example above)
2. Query the nonce before sending, and then manually increment on each transaction (passing it through via nonce: ...)

Example of the first (as detailed in the above link) -

for (let i = 0; i < 10; i++) {
  const txhash = await api.tx.balances
    .transfer(recipient, 123)
    .signAndSend(sender, { nonce: -1 })
}

Example of the second approach, manually incrementing -

// or get it via system.account, not taking the txpool into account
let nonce = await api.rpc.system.accountNextIndex(sender)

for (let i = 0; i < 10; i++) {
  const txhash = await api.tx.balances
    .transfer(recipient, 123)
    .signAndSend(sender, { nonce })
  nonce = nonce.addn(1)

}