Here is an article about the problem you are having when hosting Bitcoin Core JSON-RPC:

Ethereum: RPC JSON outside of localhost, Bitcoin Core configuration issues

When running Bitcoin Core (BTC) as a server, you often encounter problems accessing JSON-RPC endpoints outside of the local machine. In this article, we will explore why you might be experiencing this issue and offer some solutions.

Why is this happening?

The problem lies in how Bitcoin Core handles RPC connections. By default, it listens on localhost:8333 (or 127.0.0.1:8333 for IPv4). However, when attempting to access the JSON-RPC endpoint outside of this local connection, Bitcoin Core attempts to connect to ip_address:8333, where ip_address is a randomly generated, system-assigned IP address.

Bitcoin.conf configuration

Your Bitcoin.conf file will look like this:

testnet=1
server=1
daemon=1
listen=1

Note that there is no option to specify an alternate IP address or port for JSON-RPC connections. This is a default setting and only applies to RPC connections.

Why isn’t it working?

When you try to access the JSON-RPC endpoint outside of “localhost”, Bitcoin Core uses its internal IP address (or 0.0.0.0 in IPv4) as the destination host and port number. This is because the default settings do not explicitly allow alternate hosts or ports.

Solutions:

To solve this problem, you have a few options:

• Use ip_address:8333 instead of just 8333:

You can modify your Bitcoin.conf file to use an alternate IP address as specified in the JSON RPC endpoint:

testnet=1
server=1
daemon=1
listen=0.0.0.0 
listen on all available network interfaces
rpcip="192.168.1.100" 
specify a different IP address
rpcport=8333 
specify the port number

Rest of your configuration...

In this example, we use 0.0.0.0 to listen on all available network interfaces and then specify an alternate IP address (192.168.1.100) for the RPC connection.

• Use a DNS-based configuration:

Alternatively, you can configure Bitcoin Core to use a DNS-based approach that allows your computer to obtain its actual IP address:

testnet=1
server=1
daemon=1
listen=0.0.0.0
dns-addr="example.com"

In this case, you need to make sure that the DNS entry example.com is resolved correctly.

• Use a different JSON-RPC port:

If you are not interested in monitoring RPC connections and want to use a specific port number for the JSON-RPC endpoint (e.g. 8545), you can specify it in your Bitcoin.conf file:

testnet=1
server=1
daemon=1
listen=0.0.0.0
rpcip="192.168.1.100"
rpcport=8545

Note that this requires changes to the JSON-RPC endpoint configuration, which may not be necessary if you use a different port number.

Conclusion:

To solve the problem of accessing Ethereum RPC endpoints outside of localhost with Bitcoin Core, consider one or more of the solutions above. By adjusting your Bitcoin.conf file or exploring alternative approaches, you should be able to resolve this issue and continue running your JSON-RPC server successfully.

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