How to attach geth to a local Parity RPC port 8545?

Question

I'm running parity with the --jsonrpc flag which listens on port 8545 by default.

I'm trying to attach a geth instance, like described in the the docs:

Attach a console to a running geth instance. By default this happens over IPC on the default IPC endpoint but when necessary a custom endpoint could be specified:

geth attach                   # connect over IPC on default endpoint
geth attach ipc:/some/path    # connect over IPC on custom endpoint
geth attach http://host:8545  # connect over HTTP
geth attach ws://host:8546    # connect over websocket

But I get a fatal error:

Fatal: Unable to attach to geth node - Invalid endpoint

This is my tested commands:

 ~ $ geth attach http://127.0.0.1:8545
Fatal: Unable to attach to geth node - Invalid endpoint
 ~ $ geth attach http://localhost:8545
Fatal: Unable to attach to geth node - Invalid endpoint
 ~ $ geth attach ws://localhost:8545
Fatal: Unable to attach to geth node - Invalid endpoint

How to attach geth to a local RPC on port 8545?

Answer 1

#Via Geth:

When you run your Parity node, use the --geth flag, for example, parity --geth.

Then go into another window and run geth attach.

The output of this is:

Welcome to the Geth JavaScript console!
>

The great thing about Parity is that you don't need to worry about turning on JSON-RPC, as it's on by default.

#Via Node:

Another approach is to use the NodeJS web3 library, which provides the same functionality. From Parity Quick Start:

npm install web3
node # Enter REPL

Web3 = require("web3");
web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));

Now you can interact with Parity the same as the Javascript Console:

web3.eth.getBlockNumber().then(blockNumber => console.log(blockNumber)) // Regular Geth command, except connected to Parity
743397

Answer 2

Recently released version 1.1 of Parity supports modules/rpc_modules RPC method and allows you to geth attach <rpcaddress> (geth 1.3.6 and 1.4.0 are supported).

Release details: https://blog.ethcore.io/announcing-parity-1-1/

Examples:

Geth 1.3.6

$ geth attach rpc://localhost

Geth 1.4.0

$ geth attach http://localhost:8545

Answer 3

Summary

I don't think that you will be able to connect geth attach (version 1.3.6) to parity (version Parity/v1.0.2-beta/x86_64-linux-gnu/rustc1.7.0).

---

Details

I tested using geth attach to connect to parity --rpc and I got the following message

Fatal: Unable to initialize console - Unable to parse module response - <nil>

So I did a trace using tcpdump and the results follow.

I started parity with the following options:

parity --datadir datadir --rpc --rpcapi "web3,eth,net,personal"  --rpccorsdomain "*"

I started tcpdump using the following command (meaning dump data in ASCII format on the interface lo (127.0.0.1) and port 8545):

sudo tcpdump -A -i lo port 8545

I started geth using the following command:

geth attach rpc:http://127.0.0.1:8545

And here are the results from tcpdump (tidied):

IP localhost.38186 > localhost.8545
POST / HTTP/1.1
Host: 127.0.0.1:8545
User-Agent: Go-http-client/1.1
Content-Length: 57
Content-Type: application/json
Accept-Encoding: gzip

{"id":1,"jsonrpc":"2.0","method":"modules","params":null}

localhost.8545 > localhost.38186
HTTP/1.1 200 OK
Transfer-Encoding: chunked
Date: Tue, 26 Apr 2016 09:51:20 GMT
Access-Control-Allow-Origin: *
Content-Type: application/json; charset=utf-8
Access-Control-Allow-Headers: origin, content-type, accept
Allow: OPTIONS, POST

{"jsonrpc":"2.0","error":{"code":-32601,"message":"Method not found","data":null},"id":1}

geth is asking parity for the support modules, but parity does not understand the "modules" command, so geth gives up.

I've tried using a few different options, but the results are similar.

I traced through the source code for geth and found that cmd/geth/js.go has a welcome() method that will request from the connected RPC instance what modules are supported. This is what you would normally see when you connect geth attach to geth --rpc:

    modules: db:1.0 eth:1.0 net:1.0 web3:1.0

But parity does not seem to support this JSON-RPC method.