# Running a BigCoin Full Node / Seed Node

A full node validates and relays the BigCoin blockchain. Running one strengthens
the network, gives you a trustless view of the chain, and is required to operate
a seed node, block explorer, pool, or exchange integration.

## Network ports

| Purpose             | Mainnet | Testnet |
|---------------------|---------|---------|
| P2P (peer traffic)  | 9444    | 19555   |
| RPC (control/API)   | 9445    | (typically 19445) |

- **P2P port 9444** must be reachable from the internet for a node to accept
  incoming peers and to act as a seed.
- **RPC port 9445** should be kept **private** (localhost or trusted hosts only).
  Never expose RPC to the public internet.

---

## Sample `bigcoin.conf`

Place this in the data directory:

- Linux: `~/.bigcoin/bigcoin.conf`
- macOS: `~/Library/Application Support/BigCoin/bigcoin.conf`
- Windows: `%APPDATA%\BigCoin\bigcoin.conf`

```ini
# ---- RPC / server ----
server=1
rpcuser=bigrpc
rpcpassword=CHANGE_ME_to_a_long_random_string
# Only allow RPC from localhost (adjust CIDR carefully if remote access needed):
rpcbind=127.0.0.1
rpcallowip=127.0.0.1
rpcport=9445

# ---- P2P / networking ----
listen=1
port=9444
maxconnections=125

# ---- node behavior ----
txindex=1          # required for explorers / full tx lookups
dbcache=512        # MB of DB cache; raise for faster sync if you have RAM

# ---- peers to connect to at startup ----
addnode=67.205.154.64:9444
```

> **Security:** Use a long, random `rpcpassword`. Prefer `rpcauth` (hashed
> credentials generated by the `rpcauth.py` helper) over a plaintext
> `rpcpassword` in shared environments. Do **not** set `rpcallowip=0.0.0.0/0`.

Test it:

```bash
bigcoind -daemon
bigcoin-cli getblockchaininfo
bigcoin-cli getpeerinfo
bigcoin-cli getnetworkinfo
```

---

## Firewall and port forwarding (P2P 9444)

To accept inbound peers you must allow **TCP 9444** in.

### Linux (ufw)

```bash
sudo ufw allow 9444/tcp comment "BigCoin P2P"
# DO NOT open 9445 (RPC) to the internet
```

### Linux (firewalld)

```bash
sudo firewall-cmd --permanent --add-port=9444/tcp
sudo firewall-cmd --reload
```

### Home router / NAT

Forward external TCP **9444 -> internal-node-IP:9444**. Give the node a static
LAN IP or a DHCP reservation so the forward stays valid.

Verify reachability from outside your network (e.g. an online port checker, or
from another host):

```bash
nc -vz your.public.ip 9444
```

For testnet, substitute **19555** everywhere you see 9444.

---

## Running as a systemd service (Linux)

Create a dedicated user and directories, then a unit file.

```bash
sudo useradd -r -m -d /var/lib/bigcoind bigcoin
sudo mkdir -p /etc/bigcoin
sudo cp bigcoin.conf /etc/bigcoin/bigcoin.conf
sudo chown -R bigcoin:bigcoin /var/lib/bigcoind /etc/bigcoin
```

`/etc/systemd/system/bigcoind.service`:

```ini
[Unit]
Description=BigCoin daemon
After=network-online.target
Wants=network-online.target

[Service]
User=bigcoin
Group=bigcoin
Type=simple
ExecStart=/usr/local/bin/bigcoind \
  -conf=/etc/bigcoin/bigcoin.conf \
  -datadir=/var/lib/bigcoind \
  -pid=/run/bigcoind/bigcoind.pid
ExecStop=/usr/local/bin/bigcoin-cli -conf=/etc/bigcoin/bigcoin.conf stop
Restart=on-failure
TimeoutStopSec=120
RuntimeDirectory=bigcoind

# hardening
NoNewPrivileges=true
PrivateTmp=true
ProtectSystem=full
ProtectHome=true

[Install]
WantedBy=multi-user.target
```

Enable and start:

```bash
sudo systemctl daemon-reload
sudo systemctl enable --now bigcoind
sudo systemctl status bigcoind
journalctl -u bigcoind -f
```

> Note: run `bigcoind` **without** `-daemon` under systemd (`Type=simple`), so
> systemd manages the process directly.

---

## Adding DNS seeds and addnode peers

Nodes discover each other through:

1. **DNS seeds** — hostnames that resolve to lists of active node IPs. These are
   compiled into the client's chain parameters. For a new coin you (the
   maintainers) run a `dnsseed`-style server or use a static host and publish its
   name. Once compiled in, clients query it automatically.

2. **`addnode` entries** — explicit peers, added in `bigcoin.conf` or at runtime:

```bash
# add a peer at runtime
bigcoin-cli addnode "203.0.113.10:9444" add

# force a one-time connection attempt
bigcoin-cli addnode "198.51.100.20:9444" onetry

# inspect current peers
bigcoin-cli getpeerinfo | grep addr
```

- Use `addnode` for peers you always want to try.
- Use `connect=` (instead of `addnode=`) only if you want to connect **exclusively**
  to specific peers (disables automatic peer discovery — usually not what you
  want for a public node).

---

## Bootstrapping a small network for launch

For a brand-new coin there are no peers yet. Bring up an initial mesh:

1. **Stand up 2-5 stable seed nodes** on hosts with static public IPs (VPS is
   ideal). Give each `listen=1`, `port=9444`, and open the firewall.

2. **Cross-connect them** so they form a mesh. In each node's config:

   ```ini
   addnode=<ip-of-seed-A>:9444
   addnode=<ip-of-seed-B>:9444
   addnode=<ip-of-seed-C>:9444
   ```

3. **Publish DNS seed hostnames** (e.g. `seed1.bigcoin.example.com`) pointing at
   those IPs, and ship them in the client's chain params / default `addnode`
   list so new users auto-connect.

4. **Mine the early blocks** on at least one node (see [MINING.md](MINING.md)) so
   the chain grows and new nodes have something to sync.

5. **Monitor connectivity** with `getpeerinfo`, `getnetworkinfo`, and
   `getconnectioncount`. Aim for each seed to have multiple inbound + outbound
   peers.

6. **Document the seed list publicly** (GitHub, website) so operators and
   exchanges can add reliable `addnode` entries.

Keep at least a couple of seed nodes running 24/7 during launch — if they all go
down before the network has organic peers, new nodes cannot bootstrap.