socket hang up from clients

Multiple clients' sockets hung up simultaneously.

Logs from `juggle-ccc`, `val-val` in box2:
```
...
request to http://127.0.0.1:8700/ failed, reason: socket hang up
request to http://127.0.0.1:8700/ failed, reason: socket hang up
...
```

jsonrpc-filter hasn't printed any logs and crashed.

We need logging to inspect further.
See issue: https://github.com/CodeChain-io/jsonrpc-filter/issues/6