Develop Reference

Error: No connection could be made because the target machine actively refused it

i use this code for working with Port
https://learn.microsoft.com/en-us/dotnet/framework/network-programming/asynchronous-client-socket-example
but I get the following error.
No connection could be made because the target machine actively refused it.
Should I not connect(bind) the socket to the port?

First we have to check whether the Database service or particular service is started or Dead position
by using this command in linux terminal
service database status (or) service service-name status
If particular service status is Dead or inactive then we have to start the service by using
service service-name start
Then check the connection, it will connect Absolutely

i changd code.
Socket listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp)
listener.Bind(localEndPoint);
listener.Listen(200);
worked.But I didn't understand why I had to do this?
There is no such thing in Microsoft's code.

SocketException: Connection refused using EasyNetQ ManagementClient

I have RabbitMQ with management console installed on my machine. Web interface is working on
http://localhost:15672
When I try to access Rabbit via code, I'm getting an exception:
var mcGuest = new ManagementClient("http://localhost", "guest", "guest", 15672);
var vhost = mcGuest.GetVhost("/");
{"No connection could be made because the target machine actively
refused it [::1]:15672"}
(source code for Management Client at https://github.com/EasyNetQ/EasyNetQ.Management.Client)
I'm running Visual Studio as Administrator, getting following output when running netstat -anb:
Line 35: TCP 0.0.0.0:5672 0.0.0.0:0 LISTENING
Line 37: TCP 0.0.0.0:15672 0.0.0.0:0 LISTENING
Line 39: TCP 0.0.0.0:25672 0.0.0.0:0 LISTENING
Line 200: TCP 127.0.0.1:15672 127.0.0.1:18577 ESTABLISHED
Line 212: TCP 127.0.0.1:18577 127.0.0.1:15672 ESTABLISHED
Line 484: TCP [::]:5672 [::]:0 LISTENING
What could be the issue?

Apparently the issue is with IPv6. Could be related to my environment.
When running EasyNetQ api on Debug, IPv6 is used and I'm getting the error. When running on Release, IPv4 is used and sockets works.
The immediate solution is to use
new ManagementClient("http://127.0.0.1", "guest", "guest", 15672);
Though I still don't know why localhost and IPv6 wouldn't work. You can see IPv6 is used by the exception details - [::1] which stands for localhost IP in v6.

Network device can be pinged but no tcp connection

I have built a windows service, that connects to a local network device via tcpClient, using an IP and a portnumber. The network device streams out data, that i receive an read. That has been working for MONTHS for multiple setups (Always 1 machine->1 network device).
Now recently almost all the connection-attempts started failing!
The weired thing is, that i can still ping the device via command prompt.
In putty, no data is transferred.
With netstat i didn't see any remote-adress listed.
In my service there is the following error-log message:
Exception by Establishing TCP/IP Connection#ServiceName System.Net.Sockets.SocketException (0x80004005): A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond XXX.XXX.XXX.XX:XXXX (translated into english ;D)
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Connect(EndPoint remoteEP)
at System.Net.Sockets.TcpClient.Connect(IPEndPoint remoteEP)
at System.Net.Sockets.TcpClient.Connect(IPAddress address, Int32 port)
Is this network-related? Or has it to do with windows-updates or anything?
My up-to-recently working code
public void readDevice()
{
TcpClient Client = new TcpClient();
System.Net.IPAddress ip = System.Net.IPAddress.Parse(ConfigurationManager.AppSettings["IP"]);
/*
* Establishing TCP/IP Connection
*/
try
{
// IP and Port number
log.Debug("Try Client.Connect:" + ip);
Client.Connect(ip, 5000);
}
catch (Exception ex)
{
/* Handle the socket exception.... */
//this error is thrown
log.Debug("Exception by Establishing TCP/IP Connection#ServiceName "+ ex);
}
NetworkStream MessageStream = Client.GetStream();
//Magic be here
}
I am really stuck, because of the ping-able but not connectable device.
Any help greatly appreciated

I don't know how much help this will be, but it sounds like a network problem. If it just stopped working and nothing has changed code wise, I would start investigating there.
I had an issue like this with a server of mine, and the problem ended up being that the port forwarding tables got messed up so I was trying to connect to the wrong machine. I just fixed the forwarding, and blam-o! Everything worked great.
I hope your problem is as easy to solve.

TCP server/client connection issue C#

so I am currently programming a simple server/client to play some basic games i did in the past.
The problem is that I can only connect while I'm on the same computer, and not via LAN (as I would want it to work), here's the code I'm working with:
Server:
IPEndPoint Ep = new IPEndPoint(IPAddress.Any, 8000);
listener = new TcpListener(Ep);
listener.Start();
Client:
IPAddress direc = IPAddress.Parse(ipManager);
Ep = new IPEndPoint(direc, 8000);
The problem is that when I try connect from another computer (connected to the same Wi-Fi obviously) I get the following error:
A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 192.168.0.5:8000
I shuold also add that this is the code when I try to connect:
Sever:
TcpClient client = listener.AcceptTcpClient();
Client:
client.Connect(Ep);
Apparently when I am connecting the server never "accepts" the connection, but I haven't been able to figure out why's that.

Since it works locally, you are probably using 127.0.0.1 or localhost as the server's listening interface. Try using 0.0.0.0 so it will listen on all interfaces or specify the IP address of the interface you want the server to listen on.

Try to connect to the port using telnet or netcat. Check if the port is accessible.
$ nc 192.168.0.5 8000
$ telnet 192.168.0.5 8000

How to test a remote UDP Port

I am looking for a simple way to see if a remote UDP port is open on a server

BEWARE that several firewalls/network setups/IDS etc. might influence the result... the following method is NOT 100% reliable but it is the only method possible with UDP IMHO (since UDP is connectionless).
You can use UdpClient, set a receive timeout on the underlying socket, make a connection to that remote server/port, Send some small message (byte[] !) and call Receive.
IF the port is closed you get an exception saying that the connection was forcibly closed (SocketException with ErrorCode 10054 = WSAECONNRESET)... which means the port is NOT open.
Otherwise you either receive an answer OR a timeout exception - both should be interpreted as "the UDP port is open".

You can not. That is by design because UDP is connectionless. You have to solve that on application layer.