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system.net.sockets.socketexception the remote server closed connection

I have this code on my server side.
public static void Data_IN(object cSocket)
{
Socket clientSocket = (Socket)cSocket;
byte[] Buffer;
int readBytes;
while (true)
{
Buffer = new byte[clientSocket.SendBufferSize];
readBytes = clientSocket.Receive(Buffer);
if (readBytes > 0)
{
Packet p = new Packet(Buffer);
DataManager(p);
}
}
}
And the main problem is that when I stop debugging the code the server always crashes and says
System.Net.Sockets.SocketException: the remote server closed connection
The error is always at readBytes = clientSocket.Recieve(Buffer);
That is the only way I can crash the server, my only concern is when someone uses the chat program that I have created and his/hers computer crashes the chat server will go down and I always need to restart the server.
Clientside code below which executes when closing the window
private void MainWindow_Closed(object sender, EventArgs e)
{
if (isConnected)
{
Packet p = new Packet(PacketType.CloseConnection, ID);
p.data.Add(login);
p.data.Add("exits from chat");
socket.Send(p.ToBytes());
socket.Close();
isConnected = false;
thread.Abort();
}
}
On below there is the code part which uses data_in, that code is on the client side
private void ConnectBtn_Click(object sender, RoutedEventArgs e)
{
if (string.IsNullOrWhiteSpace(Login.Text))
{
MessageBox.Show("Add username");
}
else if (!IPAddress.TryParse(serverIP.Text, out ipAdress))
{
MessageBox.Show("Add valid ip");
}
else
{
ClearRequireMsg();
socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint ipEndPoint = new IPEndPoint(ipAdress, 4242);
try
{
socket.Connect(ipEndPoint);
login = Login.Text;
isConnected = true;
ConnectBtn.IsEnabled = false;
SendBtn.IsEnabled = true;
thread = new Thread(Data_IN);
thread.Start();
}
catch (SocketException ex)
{
AddMsgToBoard("Error during connecting to server", "System");
}
}
}

You're calling the function Data_IN without passing any parameter.
thread = new Thread(Data_IN);
Right way:
new Thread(() => Data_IN(socket));

Using UdpClient, how do you retry UdpClient.Connect() until it succeeds?

My client/server programs work well with each other, but only when the server is up and running before my client starts. If the client fails to connect on the first try, I can't get it to try again.
Here's my Client's connect method.
public void connect()
{
IPAddress server_address = IPAddress.Parse("127.0.0.1");
IPEndPoint server_ip = new IPEndPoint(server_address, 5685);
Console.WriteLine("2");
bool connected = false;
while (!connected)
{
try
{
Console.WriteLine("IN CONNECTED");
udp_client.Connect(server_ip);
byte[] send_data = Encoding.ASCII.GetBytes("INIT");
udp_client.Send(send_data, send_data.Length);
byte[] received_bytes = udp_client.Receive(ref server_ip);
string received_data = Encoding.ASCII.GetString(received_bytes);
if (received_data == "INIT")
{
connected = true;
Console.WriteLine("RECEIVED INIT");
listen(server_ip);
}
}
catch (Exception e)
{
Console.WriteLine(e);
}
}
}
What I was hoping to see is the udp_client.Connect(server_ip) to loop until I received that "INIT" message from the server.
As it currently stands, there is no loop. It seems to get stuck on udp_client.Receive(ref server_ip).
Any help would be appreciated!

This is pseudoCode - you will have to move somethings to class scope to allow future send/receives (which you'd do using a different method). This is only designed to show you how to connect when the connection blocks:
bool isClientConnected = false;
var connector = new System.ComponentModel.BackgroundWorker();
public void connectToUDP(){
connector.DoWork+= connect;
connector.RunWorkerAsync();
}
private void connect(object sender, DoWorkEventArgs e)
{
IPAddress server_address = IPAddress.Parse("127.0.0.1");
IPEndPoint server_ip = new IPEndPoint(server_address, 5685);
Console.WriteLine("2");
try
{
Console.WriteLine("Waiting for server...");
udp_client.Connect(server_ip);
byte[] send_data = Encoding.ASCII.GetBytes("INIT");
udp_client.Send(send_data, send_data.Length);
byte[] received_bytes = udp_client.Receive(ref server_ip);
string received_data = Encoding.ASCII.GetString(received_bytes);
if (received_data == "INIT")
{
isClietConnected = true;
Console.WriteLine("now connected");
listen(server_ip);
}
catch (Exception e)
{
Console.WriteLine(e);
}
}
public bool sendReceiveUDP(string send){
if(!isClientConnected){
return false;
}
//perform send
return true;
}
You would then maintain the connected session using class scope and send/receive using a different method. This is for connect only since you only need to do it once.
How you set something like this up:
private bool isConnected = false();
private bool send(){
if(!isConnected){
connect();
}
//send
}
private bool connect(){
if(!isConnected){
//launch connection thread
}
}
private delegate void onNewReceive(string message);
public event onNewReceive onNewReceiveEvent;
public void fireEvent(string message){
onNewReceiveEvent.Invoke(message);
}
private void waitForData(object sender, DoWorkEventArgs e){
//this is the backgroundworker
while(true){
receive();
fireEvent(message);
}
}
Then, subscribe to the onNewREceivedEvent in another class and process the inbound message. onNewReceivedEvent += processInboundMEsasage();
This is all psuedocode and "brain compiled" (creit to others) so it's only meant for demonstrations. Without intellisense, I'm lost.

How to change status of label when a sql server goes down

I have this block of code in my c# application:
private bool connected
public void ChangeStatusa()
{
if(connected)
{
label1.Text="Connected"
}else{
label1.Text="Connected"
}
}
I want to auto execute this code when the sql server is disconnected,
and I want to do this work in the background without affecting my application performance.
Essentially, I want to create a system in my application which is responsible for checking the sql server connectivity, and auto change the status when the connection is lost.

Are you connecting via tcp? if so you could try using a straight socket connection with an async receive : here's some code :
class Program
{
static bool disc = false;
static void Main(string[] args)
{
dbtest dt = new dbtest();
dt.Disconnected += new EventHandler(dt_Disconnected);
dt.Start("10.1.32.97", 1433);
while (!Console.KeyAvailable)
{
Console.WriteLine(disc?"disconnected":"tick");
Thread.Sleep(2000);
}
dt.Stop();
}
static void dt_Disconnected(object sender, EventArgs e)
{
disc = true;
Console.WriteLine("Disconnected");
}
}
public class dbtest
{
byte[] buffer = new byte[10];
Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
public event EventHandler Disconnected = null;
public void Start(string host, int port)
{
if(s!=null)
{
Stop();
}
s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
s.Connect(host, port);
Console.WriteLine("Connected.");
s.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, ReceiveCallBack, s);
}
public void Stop()
{
if (s != null)
{
s.Close();
s.Dispose();
s = null;
}
}
void ReceiveCallBack(IAsyncResult ar)
{
Socket s = ar as Socket;
if (s != null && s.Connected)
{
int rcvd = s.EndReceive(ar);
if (rcvd > 0)
{
s.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, ReceiveCallBack, s);
return;
}
}
if(Disconnected!=null)
Disconnected(this, EventArgs.Empty);
}
}
This is just basic - I'm not sure how long sql server will keep hold of a socket that hasn;t responded. Maybe add a count - reconnect on disconnect to see if its actually a real disconnect etc etc ...

Sounds like a Timer would work for this purpose. Background thread in an infinite loop with a thread sleep would also work but I dont like anything in an infinite loop.
See
C# Background Thread
Here is a fxn to check your connection
namespace answer1
{
using System.ComponentModel;
using System.Data.SqlClient;
internal class ConnectionCheck
{
private BackgroundWorker bw = new BackgroundWorker();
private void CheckConnection()
{
string connetionString = null;
SqlConnection cnn;
connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
cnn = new SqlConnection(connetionString);
try
{
cnn.Open();
Console.WriteLine("Connection Open ! ");
cnn.Close();
}
catch (Exception ex)
{
Console.WriteLine("Can not open connection ! ");
}
}
private void bw_DoWork(object sender, DoWorkEventArgs e)
{
while (true)
{
CheckConnection();
System.Threading.Thread.Sleep(5000);
}
}
/// <summary>
/// This is the Main routine you call to execute the background thread
/// </summary>
public void RunBackgroundSQLCheck()
{
bw.DoWork += this.bw_DoWork;
bw.RunWorkerAsync();
}
}
}

How to Implement Wait function in windows Phone 7.1

I want to connect to a server using Ip address from client. To get the Ip address of server I am using below code, It detecting the server correctly but I want to perform some other function after HostEndPoint variable set by event handler untill that I need to make wait How can I implement it? .. Below code used to scan is Proper way? If not how?
Thanks
int startIp = 0;
int EndIp = 255;
int HostPort = 4678;
string = ipPrefix = "192.168.1.";
EndPoint HostEndPoint;
private void ScanHosts()
{
Socket clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
for (startIP = 0; startIP <= endIP; startIP++)
{
DnsEndPoint endPoint = new DnsEndPoint(ipPrefix + startIP.ToString(), HostPort);
try
{
SocketAsyncEventArgs socketEventArgs = new SocketAsyncEventArgs();
socketEventArgs.RemoteEndPoint = endPoint;
socketEventArgs.UserToken = clientSocket;
socketEventArgs.Completed += new EventHandler<SocketAsyncEventArgs>(socketEventArgs_Connected);
clientSocket.ConnectAsync(socketEventArgs);
}
catch { }
}
}
private void socketEventArgs_Connected(object sender, SocketAsyncEventArgs e)
{
if (e.SocketError == SocketError.Success)
{
HostEndPoint = e.RemoteEndPoint;
}
}

You can use AutoResetEvent for it. FE my usage:
AutoResetEvent autoResetLoadDiscTitleAndPersonalDataById = new AutoResetEvent(false);
DataService.LoadDiscTitleAndPersonalDataById(titleToSync.id_on_server, titleInfoXML =>
{
Title TitleInfo = new Title(titleInfoXML);
TitleInfo.UpdateToDb();
autoResetLoadDiscTitleAndPersonalDataById.Set();
});
autoResetLoadDiscTitleAndPersonalDataById.WaitOne();

How do I get all servers' IP which are listening on specific port LAN?

How do I get all servers IP which are listening on specific port (Ex:9090) in LAN
I have already read some basics information about multicast,anycast ,unicast and broadcast and it seems like broadcast is the one meant for my application.
I am thinking of two ideas .. Use TCP protocol to Connect to all IP Addresses (192.168.1.1-254) in parallel on port 9090 and set a little time period to the connection timeout. just to check if there's any responce. (but it doesn't seem like a good idea)Use UDP protocol and broadcast a message like "hello" and check for response then get all IP Addresses which respond.
So which idea should I pick, are there better ideas to do it?
I would also like to know if my broadcast-ed message is received to the server and how to get the IP address of it.

I've done it with TCP to search all server that is listening on a specific port.
Its not an idle solution, but it worked for me.
I've created a userControl with a public function Initialize to pass the port that i want to scan for servers.
public ServerDiscovery()
{
InitializeComponent();
// statusLabel.Image = imageState.Images[2];
timer.Elapsed += timer_tick;
}
int port = 0;
bool busy = false; // to tell that the function is busy with scanning.
public void Initialize(int port)
{
this.port = port;
}
System.Timers.Timer timer = new System.Timers.Timer(5000);
List<SocketAsyncEventArgs> list = new List<SocketAsyncEventArgs>();
// this list to hold all sockets that created to connect to IP .. to DISPOSE it later
HashSet<string> usedIP = new HashSet<string>();
//usedIP will be explained later.
public IPEndPoint getAddress()
{ //this function to get the IPEndPoint of the selected server from listview.
if (listServer.SelectedItems.Count > 0)
{
if (listServer.SelectedItems[0].ImageIndex == 0)
{
ListViewItem item = listServer.SelectedItems[0];
IPEndPoint ep = new IPEndPoint(IPAddress.Parse(item.SubItems[1].Text), port);
return ep;
}
}
return null;
}
public void Refresh() //to scan for servers
{
if (!busy)
{
usedIP.Clear();
listServer.Items.Clear();
// statusLabel.Text = "Scanning for servers.";
// statusLabel.Image = Image.FromFile("loading.gif");
// btnRefresh.Enabled = false;
busy = true;
timer.Start();
IPAddress[] IpA = Dns.GetHostByName(Dns.GetHostName()).AddressList;
for (int j = 0; j < IpA.Length ; j++)
{
if (IpA[j].AddressFamily == AddressFamily.InterNetwork) // to make sure it's an IPV4
{
string scanIP = IpA[j].ToString().Substring(0, IpA[j].ToString().LastIndexOf(".")) + ".";
if (!usedIP.Contains(scanIP))
//usedIP is a hashset that holds the first 3 parts on an ip (ex:"192.168.1." from "192.168.1.30") i used this to avoid scanning the same ip addresses more than once .. like if i had a wireless network ip ("192.168.1.5") and an Ethernet Network ip ("192.168.1.5"). so with that hashset it will scan once.
{
usedIP.Add(scanIP);
Parallel.For(1, 255, i =>
{
Scan(scanIP + i);
});
}
}
}
}
}
private void Scan(string ipAdd)
{
Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
SocketAsyncEventArgs e = new SocketAsyncEventArgs();
e.RemoteEndPoint = new IPEndPoint(IPAddress.Parse(ipAdd), port);
e.UserToken = s;
e.Completed += new EventHandler<SocketAsyncEventArgs>(e_Completed);
list.Add(e); // add the created socket to a list to dispose when time is up.
s.ConnectAsync(e);
}
private void e_Completed(object sender, SocketAsyncEventArgs e)
{
if (e.ConnectSocket != null) //if there's a responce from the server [e.ConnectSocket] will not be equal null.
{
StreamReader sr = new StreamReader(new NetworkStream(e.ConnectSocket));
ListViewItem item = new ListViewItem();
string[] cmd = sr.ReadLine().Split('<'); in my server constructor this line will receive a string like "PC_NAME<Available" ..
item.Text = cmd[0];
item.SubItems.Add(((IPEndPoint)e.RemoteEndPoint).Address.ToString());
item.SubItems.Add(cmd[1]);
if (cmd[1] == "Busy")
item.ImageIndex = 1;
else
item.ImageIndex = 0;
AddServer(item);
list.Remove(e); //active server should be remove from the list that holds the sockets and disposed.. because there's no need to keep connection after showing that this server is active.
((Socket)e.UserToken).Dispose();
}
}
delegate void AddItem(ListViewItem item);
private void AddServer(ListViewItem item)
{
if (InvokeRequired)
{
Invoke(new AddItem(AddServer), item); //just to add an item from a background thread.
return;
}
listServer.Items.Add(item);
}
private void timer_tick(object sender, EventArgs e)
{
busy = false; //when time's up .. set busy to false so we can scan again
timer.Stop();
foreach (var s in list) //dispose all sockets that's trying to connect and waiting for a response
{
try
{
((Socket)s.UserToken).Dispose();
}
catch { }
}
//this.Invoke((MethodInvoker)delegate // for design
// {
// btnRefresh.Enabled = true;
// btnRefresh.BorderStyle = Border3DStyle.Raised;
// statusLabel.Text = "Ready.";
// statusLabel.Image = imageState.Images[2];
// });
}
private void btnRefresh_Click(object sender, EventArgs e)
{
// btnRefresh.BorderStyle = Border3DStyle.Sunken;
Refresh();
}
// private void listServer_KeyUp(object sender, KeyEventArgs e)
// {
// if (e.KeyCode == Keys.F5)
// {
// btnRefresh_Click(sender, (EventArgs)e);
// }
// }
}
Again this's not an ideal solution that works on any case but it worked fine with me.