154 lines
5.9 KiB
Markdown
154 lines
5.9 KiB
Markdown
---
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title: Connecting to the network
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---
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## How Peers Are Found
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Geth continuously attempts to connect to other nodes on the network
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until it has peers. If you have UPnP enabled on your router or run
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ethereum on an Internet-facing server, it will also accept connections
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from other nodes.
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Geth finds peers through something called the discovery protocol. In
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the discovery protocol, nodes are gossipping with each other to find
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out about other nodes on the network. In order to get going initially,
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geth uses a set of bootstrap nodes whose endpoints are recorded in the
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source code.
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To change the bootnodes on startup, use the `--bootnodes` option and
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separate the nodes by commas. For example:
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geth --bootnodes enode://pubkey1@ip1:port1,enode://pubkey2@ip2:port2,enode://pubkey3@ip3:port3
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## Common Problems With Connectivity
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Sometimes you just can't get connected. The most common reasons are
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as follows:
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- Your local time might be incorrect. An accurate clock is required
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to participate in the Ethereum network. Check your OS for how to resync
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your clock (example sudo ntpdate -s time.nist.gov) because even 12
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seconds too fast can lead to 0 peers.
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- Some firewall configurations can prevent UDP traffic from flowing.
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You can use the static nodes feature or `admin.addPeer()` on the console
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to configure connections by hand.
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To start geth without the discovery protocol, you can use the `--nodiscover` parameter. You only want this is you are running a test node or an experimental test network with fixed nodes.
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## Checking Connectivity
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To check how many peers the client is connected to in the interactive console, the `net` module has two attributes give you info about the number of peers and whether you are a listening node.
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```js
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> net.listening
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true
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> net.peerCount
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4
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```
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To get more information about the connected peers, such as IP address and port number, supported protocols, use the `peers()` function of the `admin` object. `admin.peers()` returns the list of currently connected peers.
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```
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> admin.peers
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[{
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ID: 'a4de274d3a159e10c2c9a68c326511236381b84c9ec52e72ad732eb0b2b1a2277938f78593cdbe734e6002bf23114d434a085d260514ab336d4acdc312db671b',
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Name: 'Geth/v0.9.14/linux/go1.4.2',
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Caps: 'eth/60',
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RemoteAddress: '5.9.150.40:30301',
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LocalAddress: '192.168.0.28:39219'
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}, {
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ID: 'a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c',
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Name: 'Geth/v0.9.15/linux/go1.4.2',
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Caps: 'eth/60',
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RemoteAddress: '52.16.188.185:30303',
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LocalAddress: '192.168.0.28:50995'
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}, {
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ID: 'f6ba1f1d9241d48138136ccf5baa6c2c8b008435a1c2bd009ca52fb8edbbc991eba36376beaee9d45f16d5dcbf2ed0bc23006c505d57ffcf70921bd94aa7a172',
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Name: 'pyethapp_dd52/v0.9.13/linux2/py2.7.9',
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Caps: 'eth/60, p2p/3',
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RemoteAddress: '144.76.62.101:30303',
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LocalAddress: '192.168.0.28:40454'
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}, {
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ID: 'f4642fa65af50cfdea8fa7414a5def7bb7991478b768e296f5e4a54e8b995de102e0ceae2e826f293c481b5325f89be6d207b003382e18a8ecba66fbaf6416c0',
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Name: '++eth/Zeppelin/Rascal/v0.9.14/Release/Darwin/clang/int',
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Caps: 'eth/60, shh/2',
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RemoteAddress: '129.16.191.64:30303',
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LocalAddress: '192.168.0.28:39705'
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} ]
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```
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To check the ports used by geth and also find your enode URI run:
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```
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> admin.nodeInfo
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{
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Name: 'Geth/v0.9.14/darwin/go1.4.2',
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NodeUrl: 'enode://3414c01c19aa75a34f2dbd2f8d0898dc79d6b219ad77f8155abf1a287ce2ba60f14998a3a98c0cf14915eabfdacf914a92b27a01769de18fa2d049dbf4c17694@[::]:30303',
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NodeID: '3414c01c19aa75a34f2dbd2f8d0898dc79d6b219ad77f8155abf1a287ce2ba60f14998a3a98c0cf14915eabfdacf914a92b27a01769de18fa2d049dbf4c17694',
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IP: '::',
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DiscPort: 30303,
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TCPPort: 30303,
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Td: '2044952618444',
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ListenAddr: '[::]:30303'
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}
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```
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## Custom Networks
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Sometimes you might not need to connect to the live public network,
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you can instead choose to create your own private testnet. This is
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very useful if you don't need to test external contracts and want just
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to test the technology, because you won't have to compete with other
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miners and will easily generate a lot of test ether to play around
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(replace 12345 with any non-negative number):
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geth -—networkid="12345" console
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It is also possible to run geth with a custom genesis block from a JSON file
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by supplying the `--genesis` flag. The genesis JSON file should have the following
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format:
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```js
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{
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"alloc": {
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"dbdbdb2cbd23b783741e8d7fcf51e459b497e4a6": {
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"balance": "1606938044258990275541962092341162602522202993782792835301376"
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},
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"e6716f9544a56c530d868e4bfbacb172315bdead": {
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"balance": "1606938044258990275541962092341162602522202993782792835301376"
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},
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...
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},
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"nonce": "0x000000000000002a",
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"difficulty": "0x020000",
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"mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
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"coinbase": "0x0000000000000000000000000000000000000000",
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"timestamp": "0x00",
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"parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
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"extraData": "0x",
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"gasLimit": "0x2fefd8"
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}
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```
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## Static nodes
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Geth also supports a feature called static nodes if you have certain
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peers you always want to connect to. Static nodes are re-connected
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on disconnects. You can configure permanent static nodes by putting something like
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the following into `<datadir>/geth/static-nodes.json`:
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```js
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[
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"enode://f4642fa65af50cfdea8fa7414a5def7bb7991478b768e296f5e4a54e8b995de102e0ceae2e826f293c481b5325f89be6d207b003382e18a8ecba66fbaf6416c0@33.4.2.1:30303",
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"enode://pubkey@ip:port"
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]
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```
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You can also add static nodes at runtime via the js console using [`admin.addPeer()`](../interface/JavaScript-Console#addpeer):
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```js
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admin.addPeer("enode://f4642fa65af50cfdea8fa7414a5def7bb7991478b768e296f5e4a54e8b995de102e0ceae2e826f293c481b5325f89be6d207b003382e18a8ecba66fbaf6416c0@33.4.2.1:30303")
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```
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Caveat: Currently the console is lacking support for removing a peer, increasing peercount or adding a non-static peer but not to keep try reconnecting.
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