Q:

Error Domain=NSCocoaErrorDomain Code=3840 "Invalid value around character 0

Hi I am new at swift and I got problem, I made a request to server with post method and I get response with good Json, after that I am makeing another request with get method but I get this error.
Error:
responseSerializationFailed(Alamofire.AFError.ResponseSerializationFailureReason.jsonSerializationFailed(Error Domain=NSCocoaErrorDomain Code=3840 "Invalid value around character 0." UserInfo={NSDebugDescription=Invalid value around character 0.})
Parameters for request:
static func getInformationFromConfig(token: String, config: String, section : String, option: String) -> [String:Any] {

        let getInformationFromConfigparam: [String : Any] = ["jsonrpc": "2.0",
                                      "id": 1,
                                      "method": "call",
                                      "params": [ token, "uci", "get", [ "config": config, "section": section, "option": option]]
    ]

    return getInformationFromConfigparam
}

 public func device(token: String, loginCompletion: @escaping (Any) -> ()) {
    let deviceinfo = JsonRequests.getInformationFromConfig(token: token, config: "wireless", section: "@wifi-iface[0]", option: "mode")
    makeWebServiceCall(urlAddress: URL, requestMethod: .get, params: deviceinfo, completion: { (JSON : Any) in
        loginCompletion(JSON)
    })
}

Request:
private func makeWebServiceCall (urlAddress: String, requestMethod: HTTPMethod, params:[String:Any], completion: @escaping (_ JSON : Any) -> ()) {

    Alamofire.request(urlAddress, method: requestMethod, parameters: params, encoding: JSONEncoding.default).responseJSON{ response in

        switch response.result {
        case .success(let value):

            let json = JSON(value)

            if let jsonData = response.result.value {

                completion(jsonData)
            }

        case .failure(let error):

                completion("Failure Response: \(error)")

ResponseString response:
 [Request]: GET http://192.168.1.1/ubus
[Response]: <NSHTTPURLResponse: 0x60000003c4a0> { URL: http://192.168.1.1/ubus } { status code: 400, headers {
Connection = "Keep-Alive";
"Content-Type" = "text/html";
"Keep-Alive" = "timeout=20";
"Transfer-Encoding" = Identity;
} }
[Data]: 35 bytes
    [Result]: FAILURE:     responseSerializationFailed(Alamofire.AFError.ResponseSerializationFailureReason.jsonSerializationFailed(Error Domain=NSCocoaErrorDomain Code=3840 "Invalid value around character 0." UserInfo={NSDebugDescription=Invalid value around character 0.}))

A:

The Error saying that the response from server is not a valid JSON string. Can you try responseString instead of responseJSON like
Alamofire.request(urlAddress, method: requestMethod, parameters: params).responseString{ response in
    debugPrint(response)
}

See the Xcode debugger output & change it according to your need.

