RPC — Remote Procedure Call

const { Connection, PublicKey } = require('@solana/web3.js');
const connection = new Connection('https://api.mainnet-beta.solana.com');

// Get account balance
const balance = await connection.getBalance(
  new PublicKey('YourWalletAddress')
);
console.log(`Balance: ${balance / 1e9} SOL`);

// Get full account info
const accountInfo = await connection.getAccountInfo(
  new PublicKey('YourAccountAddress')
);

// Get multiple accounts in one call (more efficient)
const accounts = await connection.getMultipleAccountsInfo([
  new PublicKey('Address1'),
  new PublicKey('Address2'),
]);

// Get transaction by signature
const tx = await connection.getTransaction(
  'YourTransactionSignature',
  { maxSupportedTransactionVersion: 0 }
);

// Get signatures for an address (paginated)
const signatures = await connection.getSignaturesForAddress(
  new PublicKey('YourAddress'),
  { limit: 100 }
);

// Get recent block
const block = await connection.getBlock(slot, {
  maxSupportedTransactionVersion: 0,
  transactionDetails: 'full',
});

const { Transaction, SystemProgram, sendAndConfirmTransaction } = require('@solana/web3.js');

const transaction = new Transaction().add(
  SystemProgram.transfer({
    fromPubkey: sender.publicKey,
    toPubkey: recipient,
    lamports: 1000000, // 0.001 SOL
  })
);

// Get latest blockhash for transaction validity
const { blockhash, lastValidBlockHeight } = 
  await connection.getLatestBlockhash();
transaction.recentBlockhash = blockhash;
transaction.feePayer = sender.publicKey;

const signature = await sendAndConfirmTransaction(
  connection, transaction, [sender]
);

// Subscribe to account changes
const subscriptionId = connection.onAccountChange(
  new PublicKey('AccountToWatch'),
  (accountInfo, context) => {
    console.log('Account updated:', accountInfo.lamports);
  },
  'confirmed'
);

// Subscribe to new slots
const slotSubscription = connection.onSlotChange((slotInfo) => {
  console.log('New slot:', slotInfo.slot);
});

// Subscribe to logs for a program
const logsSubscription = connection.onLogs(
  new PublicKey('ProgramId'),
  (logs) => {
    console.log('Program logs:', logs.logs);
  }
);