Ethereum: unable to call RPC API from another machine on the same LAN
As an Ethereum developer, you’re probably familiar with the importance of interacting with your blockchain network using remote procedure calls (RPC). However, one common problem arises when trying to call the RPC API on a node running on the same local network as the other machine. In this article, we will consider why this problem occurs and offer possible solutions.
Problem:
When you run a Regtest node on your local network, it’s an autonomous environment running an Ethereum node with limited access control. However, when you try to call the RPC API from other machines on the same local network, you encounter an obstacle.
In particular, the rpcallowip option is disabled by default for Regtest nodes running on the same local network. This means that when you try to make requests to another machine’s Ethereum node using RPC, you will receive an error.
The rpcallowip option:
In Ethereum Core 1.x and earlier, the rpcallowip option controls access rights for the RPC API on your node. If set to true', it allows RPC calls from outside the local network (ie from another machine). However, in Regtest mode, this option is disabled by default.
Why is this happening?
The reason for this behavior lies in the architecture and security limitations of Ethereum. By design, Regtest nodes are isolated environments that do not need to interact with external networks. Thus, they are not bound by the same access rights as production nodes.
When you start a Regtest node on a local network, it starts an internal testnet instance that does not require RPC calls from outside the network. Therefore, therpcallowipoption is disabled to prevent unauthorized access.
Solutions:
To solve this problem and make RPC API calls from other machines on the same local network:
- Use a second network:
If you need to interact with an Ethereum node of another machine on the same local network, consider using a second network (for example,rpcuser
orrpcpassword). You can then use these options instead ofrpcallowip.
- Setrpcallowip
totrue:On your Regtest node, you can setrpcallowiptotruebefore running it on the same local network:
regtest -r -n --rpcallowip true
Be careful when using this option, as it allows RPC calls from outside the LAN.
- Use a second RPC API: Consider using the eth_getEventAddress
oreth_callmethods of the Ethereum API instead of traditional RPC calls to external nodes.
Conclusion:
Althoughrpcallowip` is intended to control access permissions for the RPC API on your host, its default behavior in Regtest mode prevents it from interacting with other machines on the same local network. By understanding why this happens and implementing one or more of these solutions, you should be able to successfully call the RPC API from other machines on the same local network.
By doing this, you will open up new opportunities for development, testing and research in your local Ethereum ecosystem!