I am running my app using real android device and in my flutter I used mysql1 to connect to localhost database. There is no problem when running the app on emulator but when comes to real device there is always a connection error. Below is my mysql.dart file:
/*This is a database configuration file*/
import 'package:mysql1/mysql1.dart';
class Mysql {
static String host = '10.0.2.2',
user = 'root', //User
db = 'users'; //Database name
static int port = 3306; //MySQL port number
Mysql();
Future<MySqlConnection> getConnection() async {
var settings = new ConnectionSettings(
host: host,
port: port,
user: user,
db: db);
return await MySqlConnection.connect(settings);
}
}
I have tried a to change the host to my localhost ip and still getting the same error. Has anyone run into the same problem?
Instead of using mysql1 ,You should have to use sqflite in flutter https://pub.dev/packages/sqflite .
I've been searching for ages and I can't seem to find a way to have a database in my spigot plugin executable, so if someone can help that would be awesome.
preferred databases:
SQLite
MySQL
You can't have (run) a database in your plugin executable. A database runs on a server and you can build up a connection to it. All SQL stuff is in the java.sql package.
You can run a database like your local minecraft server on your computer throw XAMPP.
Here is an example how you build up a connection to a local running database:
Connection connection;
String host, port, username, password, databaseName;
host = "localhost"; // enter your host (ip address)
port = "3306"; // the entering port
username = "root"; // your username
password = ""; // your password
databaseName = "database-name"; // the database name, where you want to connect to
String url = "jdbc:mysql://" + host + ":" + port + "/" + databaseName;
try {
connection = DriverManager.getConnection(url, username, password);
} catch (SQLException throwables) {
throwables.printStackTrace();
}
I suggest you to create a SQL Class in which you manage all. Maby look for a tutorial on Youtube how to use SQL in Java.
I'm trying to implement a TCP connection, everything works fine from the server's side but when I run the client program (from client computer) I get the following error:
java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:432)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
at java.net.Socket.<init>(Socket.java:375)
at java.net.Socket.<init>(Socket.java:189)
at TCPClient.main(TCPClient.java:13)
I tried changing the socket number in case it was in use but to no avail, does anyone know what is causing this error & how to fix it.
The Server Code:
//TCPServer.java
import java.io.*;
import java.net.*;
class TCPServer {
public static void main(String argv[]) throws Exception {
String fromclient;
String toclient;
ServerSocket Server = new ServerSocket(5000);
System.out.println("TCPServer Waiting for client on port 5000");
while (true) {
Socket connected = Server.accept();
System.out.println(" THE CLIENT" + " " + connected.getInetAddress()
+ ":" + connected.getPort() + " IS CONNECTED ");
BufferedReader inFromUser = new BufferedReader(
new InputStreamReader(System.in));
BufferedReader inFromClient = new BufferedReader(
new InputStreamReader(connected.getInputStream()));
PrintWriter outToClient = new PrintWriter(
connected.getOutputStream(), true);
while (true) {
System.out.println("SEND(Type Q or q to Quit):");
toclient = inFromUser.readLine();
if (toclient.equals("q") || toclient.equals("Q")) {
outToClient.println(toclient);
connected.close();
break;
} else {
outToClient.println(toclient);
}
fromclient = inFromClient.readLine();
if (fromclient.equals("q") || fromclient.equals("Q")) {
connected.close();
break;
} else {
System.out.println("RECIEVED:" + fromclient);
}
}
}
}
}
The Client Code:
//TCPClient.java
import java.io.*;
import java.net.*;
class TCPClient {
public static void main(String argv[]) throws Exception {
String FromServer;
String ToServer;
Socket clientSocket = new Socket("localhost", 5000);
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(
System.in));
PrintWriter outToServer = new PrintWriter(
clientSocket.getOutputStream(), true);
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(
clientSocket.getInputStream()));
while (true) {
FromServer = inFromServer.readLine();
if (FromServer.equals("q") || FromServer.equals("Q")) {
clientSocket.close();
break;
} else {
System.out.println("RECIEVED:" + FromServer);
System.out.println("SEND(Type Q or q to Quit):");
ToServer = inFromUser.readLine();
if (ToServer.equals("Q") || ToServer.equals("q")) {
outToServer.println(ToServer);
clientSocket.close();
break;
} else {
outToServer.println(ToServer);
}
}
}
}
}
This exception means that there is no service listening on the IP/port you are trying to connect to:
You are trying to connect to the wrong IP/Host or port.
You have not started your server.
Your server is not listening for connections.
On Windows servers, the listen backlog queue is full.
I would check:
Host name and port you're trying to connect to
The server side has managed to start listening correctly
There's no firewall blocking the connection
The simplest starting point is probably to try to connect manually from the client machine using telnet or Putty. If that succeeds, then the problem is in your client code. If it doesn't, you need to work out why it hasn't. Wireshark may help you on this front.
You have to connect your client socket to the remote ServerSocket. Instead of
Socket clientSocket = new Socket("localhost", 5000);
do
Socket clientSocket = new Socket(serverName, 5000);
The client must connect to serverName which should match the name or IP of the box on which your ServerSocket was instantiated (the name must be reachable from the client machine). BTW: It's not the name that is important, it's all about IP addresses...
I had the same problem, but running the Server before running the Client fixed it.
One point that I would like to add to the answers above is my experience-
"I hosted on my server on localhost and was trying to connect to it through an android emulator by specifying proper URL like http://localhost/my_api/login.php . And I was getting connection refused error"
Point to note - When I just went to browser on the PC and use the same URL (http://localhost/my_api/login.php) I was getting correct response
so the Problem in my case was the term localhost which I replaced with the IP for my server (as your server is hosted on your machine) which made it reachable from my emulator on the same PC.
To get IP for your local machine, you can use ipconfig command on cmd
you will get IPv4 something like 192.68.xx.yy
Voila ..that's your machine's IP where you have your server hosted.
use it then instead of localhost
http://192.168.72.66/my_api/login.php
Note - you won't be able to reach this private IP from any node outside this computer. (In case you need ,you can use Ngnix for that)
I had the same problem with Mqtt broker called vernemq.but solved it by adding the following.
$ sudo vmq-admin listener show
to show the list o allowed ips and ports for vernemq
$ sudo vmq-admin listener start port=1885 -a 0.0.0.0 --mountpoint /appname --nr_of_acceptors=10 --max_connections=20000
to add any ip and your new port. now u should be able to connect without any problem.
Hope it solves your problem.
Hope my experience may be useful to someone. I faced the problem with the same exception stack trace and I couldn't understand what the issue was. The Database server which I was trying to connect was running and the port was open and was accepting connections.
The issue was with internet connection. The internet connection that I was using was not allowed to connect to the corresponding server. When I changed the connection details, the issue got resolved.
In my case, I gave the socket the name of the server (in my case "raspberrypi"), and instead an IPv4 address made it, or to specify, IPv6 was broken (the name resolved to an IPv6)
In my case, I had to put a check mark near Expose daemon on tcp://localhost:2375 without TLS in docker setting (on the right side of the task bar, right click on docker, select setting)
i got this error because I closed ServerSocket inside a for loop that try to accept number of clients inside it (I did not finished accepting all clints)
so be careful where to close your Socket
I had same problem and the problem was that I was not closing socket object.After using socket.close(); problem solved.
This code works for me.
ClientDemo.java
public class ClientDemo {
public static void main(String[] args) throws UnknownHostException,
IOException {
Socket socket = new Socket("127.0.0.1", 55286);
OutputStreamWriter os = new OutputStreamWriter(socket.getOutputStream());
os.write("Santosh Karna");
os.flush();
socket.close();
}
}
and
ServerDemo.java
public class ServerDemo {
public static void main(String[] args) throws IOException {
System.out.println("server is started");
ServerSocket serverSocket= new ServerSocket(55286);
System.out.println("server is waiting");
Socket socket=serverSocket.accept();
System.out.println("Client connected");
BufferedReader reader=new BufferedReader(new InputStreamReader(socket.getInputStream()));
String str=reader.readLine();
System.out.println("Client data: "+str);
socket.close();
serverSocket.close();
}
}
I changed my DNS network and it fixed the problem
You probably didn't initialize the server or client is trying to connect to wrong ip/port.
Change local host to your ip address
localhost
//to you local ip
192.168.xxxx
I saw the same error message ""java.net.ConnectException: Connection refused" in SQuirreLSQL when it was trying to connect to a postgresql database through an ssh tunnel.
Example of opening tunel:
Example of error in Squirrel with Postgresql:
It was trying to connect to the wrong port. After entering the correct port, the process execution was successful.
See more options to fix this error at: https://stackoverflow.com/a/6876306/5857023
In my case, with server written in c# and client written in Java, I resolved it by specifying hostname as 'localhost' in the server, and '[::1]' in the client. I don't know why that is, but specifying 'localhost' in the client did not work.
Supposedly these are synonyms in many ways, but apparently, not not a 100% match. Hope it helps someone avoid a headache.
For those who are experiencing the same problem and use Spring framework, I would suggest to check an http connection provider configuration. I mean RestTemplate, WebClient, etc.
In my case there was a problem with configured RestTemplate (it's just an example):
public RestTemplate localRestTemplate() {
Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("localhost", <some port>));
SimpleClientHttpRequestFactory clientHttpReq = new SimpleClientHttpRequestFactory();
clientHttpReq.setProxy(proxy);
return new RestTemplate(clientHttpReq);
}
I just simplified configuration to:
public RestTemplate restTemplate() {
return new RestTemplate(new SimpleClientHttpRequestFactory());
}
And it started to work properly.
There is a service called MySQL80 that should be running to connect to the database
for windows you can access it by searching for services than look for MySQL80 service and make sure it is running
It could be that there is a previous instance of the client still running and listening on port 5000.
I'm trying to run my first IoT on my Raspberry Pi 3.
But using this code ....
public void StartServer()
{
Task.Run(async () =>
{
listener = new StreamSocketListener();
listener.Control.KeepAlive = true;
listener.Control.NoDelay = true;
await listener.BindServiceNameAsync(port.ToString());
});
}
I get this error at BindServiceNameAsync...
Exception thrown: 'System.Runtime.InteropServices.COMException' in mscorlib.ni.dll
WinRT information: Only one usage of each socket address (protocol/network address/port)
is normally permitted.
In appmanifest I have checked "Internet (Client & Server)".
Any idea why I get this error?
Thanks
Most likely the port that you are trying to use is already being used by another process. Try a different port.
I am developing an application on windows phone 8, and would like to know - Is it possible to check whether retrieved device IP address is over Wifi or carrier?
Code used to find device IP address is -
public IPAddress IdentifyDeviceIp()
{
List<string> DeviceIPAddresses = new List<string>();
var DeviceHostnames = Windows.Networking.Connectivity.NetworkInformation.GetHostNames();
foreach (var DeviceHostName in DeviceHostnames)
{
if (DeviceHostName.IPInformation != null)
{
string DeviceIpAddress = DeviceHostName.DisplayName;
// Emulator: ignore IPV6 addresses
if (DeviceIpAddress.Contains(":"))
continue;
DeviceIPAddresses.Add(DeviceIpAddress);
}
}
if (DeviceIPAddresses.Count == 0)
{
MessageBox.Show("No IP address found!!");
return new IPAddress(0);
}
return IPAddress.Parse(DeviceIPAddresses[0]);
}
To determine what a network is currently used by a phone you can check NetworkInterfaceType. Mode details here http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh487166(v=vs.105).aspx.
you can use this code for determinate where is the type of Network Interface :
NetworkInterfaceType MyNetworkInterfaceType = Microsoft.Phone.Net.NetworkInformation.NetworkInterface.NetworkInterfaceType;
If you've on Wifi, this code return "Wireless80211", you can read all documentation here
Also, with Windows Phone, you can Set your prefer NetworkInterface ( If you hove connected on Wifi and, on 3G, you can create a request with the Cellular connection (2G/3G/4G) or with NonCellular connection ( Ethernet, Wifi...) you can read this for information
You can Set your prefer Network for SocketRequest and for WebRequest you can read documentation about that in the msdn :
Microsoft.Phone.Net.NetworkInformation.WebRequestExtensions
Microsoft.Phone.Net.NetworkInformation.SocketExtensions
Use just the function
SetNetworkPreference(Socket/WebRequest, NetworkSelectionCharacteristics)
for define a request with your prefer network.
For better Experience for your application user, prefer the NonCellular DataConnection, generaly, it's faster [except for 4G] and cheaper... :D
For Your Problem, If you Set your prefer Connection, and you send a request, the ip adress use for this request must match the network defined preference.