HTTP Server & CLI

The Quick Start showed how to run DevChain in-process with CreateWeb3. When you need external tools to connect — MetaMask, Foundry, Hardhat, ethers.js, or any Ethereum client — DevChain can also run as a standalone HTTP JSON-RPC server. This is the .NET equivalent of npx hardhat node or anvil, with the same default mnemonic and compatible RPC methods.

Prerequisites

Install the server as a .NET global tool:

dotnet tool install -g Nethereum.DevChain.Server

Or add it as a project dependency for embedding:

dotnet add package Nethereum.DevChain.Server

Start the Server

Run with defaults — 10 funded accounts, port 8545, auto-mine:

nethereum-devchain

The startup banner shows all funded accounts with their addresses and private keys, just like Hardhat or Anvil:

 _   _      _   _
| \ | | ___| |_| |__   ___ _ __ ___ _   _ _ __ ___
|  \| |/ _ \ __| '_ \ / _ \ '__/ _ \ | | | '_ ` _ \
| |\  |  __/ |_| | | |  __/ | |  __/ |_| | | | | | |
|_| \_|\___|\__|_| |_|\___|_|  \___|\__,_|_| |_| |_|

              DevChain Server v7.1.0

  RPC:        http://127.0.0.1:8545
  Chain ID:   31337
  Hardfork:   amsterdam
  Gas Limit:  30,000,000
  Mining:     auto-mine (instant)
  Storage:    SQLite (auto-cleanup on exit)

  Available Accounts
  ==================
  (0) 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266 (10000 ETH)
  (1) 0x70997970C51812dc3A010C7d01b50e0d17dc79C8 (10000 ETH)
  ...

  Private Keys
  ============
  (0) 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80
  (1) 0x59c6995e998f97a5a0044966f0945389dc9e86dae88c7a8412f4603b6b78690d
  ...

  HD Wallet
  =========
  Mnemonic:        test test test test test test test test test test test junk
  Derivation Path: m/44'/60'/0'/0/x

The default mnemonic and derivation path match Hardhat and Anvil, so existing test scripts work without changes.

CLI Options

Customise the server with command-line flags:

# Custom port and more accounts
nethereum-devchain -p 8546 -a 20

# Higher account balance (in ETH)
nethereum-devchain -e 100000

# Interval mining (1 block per second)
nethereum-devchain -b 1000

# Fork mainnet
nethereum-devchain -f https://eth.llamarpc.com --fork-block 19000000

# Persistent storage
nethereum-devchain --persist ./mychain

# Fully in-memory
nethereum-devchain --in-memory

# Custom mnemonic
nethereum-devchain -m "your twelve word mnemonic phrase here"

Full Option Reference

Flag	Description	Default
-p, --port	HTTP port	8545
--host	Bind address	127.0.0.1
-a, --accounts	Number of funded accounts	10
-m, --mnemonic	HD wallet mnemonic	Hardhat default
-e, --balance	Account balance in ETH	10000
-c, --chain-id	Chain ID	31337
-b, --block-time	Block time in ms (0 = auto-mine)	0
--gas-limit	Block gas limit	30000000
-f, --fork	Fork from this RPC URL	—
--fork-block	Fork at specific block number	latest
--persist [DIR]	Persist data to disk	./chaindata
--in-memory	Use fully in-memory storage	—
-v, --verbose	Enable verbose logging	—

Connecting from External Tools

The server exposes a standard JSON-RPC endpoint at POST / and a health check at GET /.

From Nethereum (C#)

using Nethereum.Web3;
using Nethereum.Web3.Accounts;

var account = new Account("0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80");
var web3 = new Web3(account, "http://127.0.0.1:8545");

var balance = await web3.Eth.GetBalance.SendRequestAsync(account.Address);

From ethers.js

const { ethers } = require("ethers");
const provider = new ethers.JsonRpcProvider("http://127.0.0.1:8545");
const signer = new ethers.Wallet(
  "0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80",
  provider
);

From curl

curl -X POST http://127.0.0.1:8545 \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

Supported RPC Methods

DevChain supports the Ethereum JSON-RPC methods below plus development methods. There is no eth_sendTransaction handler; send signed transactions with eth_sendRawTransaction:

Category	Methods
Network	web3_clientVersion, web3_sha3, net_version, net_listening, net_peerCount, eth_chainId, eth_syncing, eth_mining, eth_coinbase, eth_accounts
Blocks	eth_blockNumber, eth_getBlockByHash, eth_getBlockByNumber, eth_getBlockTransactionCountByHash, eth_getBlockTransactionCountByNumber, eth_getBlockReceipts
Transactions	eth_sendRawTransaction, eth_getTransactionByHash, eth_getTransactionReceipt, eth_getTransactionByBlockHashAndIndex, eth_getTransactionByBlockNumberAndIndex
State	eth_getBalance, eth_getCode, eth_getStorageAt, eth_getTransactionCount
Execution	eth_call, eth_estimateGas, eth_createAccessList
Gas & Fees	eth_gasPrice, eth_maxPriorityFeePerGas, eth_feeHistory
Filters	eth_newFilter, eth_newBlockFilter, eth_getFilterChanges, eth_getFilterLogs, eth_uninstallFilter, eth_getLogs
Proofs	eth_getProof
Debug	debug_traceTransaction, debug_traceCall

Development Methods

These match Hardhat and Anvil conventions:

Method	Description
evm_mine	Mine a block
evm_snapshot	Take a state snapshot
evm_revert	Revert to a snapshot
evm_increaseTime	Advance the block timestamp
evm_setNextBlockTimestamp	Set exact next block timestamp
hardhat_setBalance	Override an account's ETH balance
hardhat_setCode	Deploy bytecode at an address
hardhat_setNonce	Set an account's nonce
hardhat_setStorageAt	Write to a contract's storage slot
hardhat_impersonateAccount	Record an address as impersonated (no signing support)
hardhat_stopImpersonatingAccount	Stop impersonating

Anvil aliases are also registered for: anvil_setBalance, anvil_setCode, anvil_setNonce, anvil_setStorageAt, anvil_mine, anvil_snapshot, anvil_revert.

Storage Modes

The server supports three storage configurations:

Mode	Flag	Blocks/TXs/Receipts/Logs	Account State and Trie Nodes	Cleanup
SQLite (default)	none	SQLite temp file	SQLite temp file	Auto-delete on exit
SQLite persistent	--persist [DIR]	SQLite at DIR/chain.db	SQLite at DIR/chain.db	Kept between restarts
In-memory	--in-memory	In-memory	In-memory	Lost on exit

Filters are always held in memory.

Use --persist when you want chain history to survive restarts. Use --in-memory for CI/CD or ephemeral test environments where speed matters most.

Embedding in ASP.NET

Instead of running the CLI, you can embed the DevChain server directly in your ASP.NET application:

using Nethereum.DevChain.Configuration;
using Nethereum.DevChain.Hosting;

var builder = WebApplication.CreateBuilder(args);

var config = new DevChainServerConfig
{
    ChainId = 31337,
    Port = 8545,
    Storage = "memory"
};

builder.AddDevChainServer(config);

var app = builder.Build();
await app.MapDevChainEndpointsAsync();
app.Run($"http://{config.Host}:{config.Port}");

AddDevChainServer registers the DevChainNode, DevAccountManager, RpcDispatcher, and all storage providers as singletons. MapDevChainEndpointsAsync starts the node and maps the JSON-RPC endpoints.

Configuration via appsettings.json

When embedding, you can also bind configuration from appsettings.json:

{
  "DevChain": {
    "ChainId": 31337,
    "Port": 8545,
    "AutoMine": true,
    "BlockTime": 0,
    "AccountCount": 10,
    "Storage": "sqlite",
    "Persist": false
  }
}

Hardhat/Anvil Migration

If you're switching from Hardhat or Anvil to DevChain:

Feature	Hardhat	Anvil	DevChain
Start command	npx hardhat node	anvil	nethereum-devchain
Default port	8545	8545	8545
Default chain ID	31337	31337	31337
Default mnemonic	Same	Same	Same
Fork support	--fork <url>	--fork-url <url>	-f <url>
Persistent storage	No	No	--persist
Interval mining	--interval <sec>	-b <sec>	-b <ms> (milliseconds)
Account impersonation	hardhat_impersonateAccount	anvil_impersonateAccount	hardhat_impersonateAccount (registered, no signing support)
Debug tracing	Limited	debug_traceTransaction	Both geth-compatible

The key difference: DevChain block time is in milliseconds, not seconds.

Next Steps

• Testing Patterns — write isolated integration tests with snapshot/revert
• Forking & State Manipulation — fork mainnet and override account state
• Debug & Trace — trace transactions at the opcode level
• For the complete server API, see the Nethereum.DevChain.Server package reference