How to covert simple RPC Call in Python to Go?

[Christian LeMoussel]

I'm having trouble translating Python code into GO.

s = socks.socksocket()
s.connect((mining_ip_conf, int(port)))  # connect to pool
connections.send(s, "getwork", 10)
work_pack = connections.receive(s, 10)
db_block_hash = (work_pack[-1][0])
diff = int((work_pack[-1][1]))
paddress = (work_pack[-1][2])
netdiff = int((work_pack[-1][3]))
s.close()

From what I understand, this code queries an RPC server and retrieves a JSON RPC response.

I tried to do this in GO.

client, err := rpc.DialHTTP("tcp", fmt.Sprintf("%s:%d", mining_ip, port))
if err != nil {
    log.Fatalf("Error in dialing. %s", err)
}

var args interface{}
var result string
err = client.Call("getwork", args, &result)
if err != nil {
    log.Fatalf("getwork", err)
}

but I've got an this error.

2017/10/10 19:36:49 Error in dialing. dial-http tcp mining_ip:port: unexpected EOF

Does anyone see anything wrong with this GO code?

[Shawn Milochik]

I think the problem is that the Python code is using a standard socket, and the Go code is using the rpc package. Try using net.Dial instead of rpc.DialHTTP.

A socket is just a socket. An rpc connection probably tries to do a bit more upon connection but isn't getting what it expects from the vanilla socket on the other side.

https://golang.org/pkg/net/#Dial

Dial returns a net.Conn, which has Read and Write methods which appear to be analogous to the send and receive methods used in the Python version.

[Bruno Albuquerque]

Yes, the server is not an http/rpc server so using DialHTTP() does not make much sense. Try with net.DialTCP() and use Write() and Read() on the returned TCPConn to send requests and get the responses.

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[Gianguido Sorà]

Since the server is communicating using JSON structures, you should unmarshal the Read() data in a struct to actually use it: https://blog.golang.org/json-and-go.

Unlike Python where JSON is typically handled through dictionaries, in Go you either provide a structure to unmarshal data to, or work your way through an  interface{} and do a lot of work using type assertion.

You can use tools like https://mholt.github.io/json-to-go/ to generate Go structs from arbitrary JSON data.

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Gianguido (gsora) Sorà

Twitter: @gsora_

GitHub: @gsora

Blog: http://blog.gsora.xyz

[Christian LeMoussel]

connections.send(s, "getwork", 10)

I searched a little bit more and here is in Python send() function

def send(sdef, data, slen):

sdef.setblocking(0)

sdef.sendall(str(len(str(json.dumps(data)))).encode("utf-8").zfill(slen))

    sdef.sendall(str(json.dumps(data)).encode("utf-8"))

Unfortunately, I don't know Python. the challenge is to rewrite the send function in Go.

[Justin Israel]

This code is converting the data to json twice.

The first time it converts it to get the length of the json string, and pad it out to the expected length (10).

The second send converts it again and just sends the encoded json string.

Your Go version would just want to encode your data as json, send and first send the length of it:

// Some Data

data := Data{"Foo"}
enc, err := json.Marshal(data)
if err != nil {

    panic(err)
}

size := fmt.Sprintf("%010d", len(data) )

// send size
// send enc

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