Cannot connect to socket on local machine - sockets

Question

I did a simple translation of the example C# code here:
let socket_CreateBindListen (sv_ : string) (pt_ : int) : Socket option =
let (he : IPHostEntry) = Dns.GetHostEntry(sv_)
let rsock, ipe =
he.AddressList
|> Seq.map (fun s ->
let (ipe2 : IPEndPoint) = new IPEndPoint (s, pt_)
let (rsock2 : Socket) = new Socket (ipe2.AddressFamily, SocketType.Stream, ProtocolType.Tcp)
rsock2.Connect ipe2 ///// <---- No connection could be made because the target machine actively refused it
rsock2, ipe2)
|> Seq.find (fun (s, t) -> s.Connected)
try
rsock.Bind ipe
rsock.Listen 10
printfn "%s now listening on port %d" sv_ pt_
Some (rsock)
with
| _ ->
printfn "Failed to connect to %s on port %d" sv_ pt_
None
socket_CreateBindListen "127.0.0.1" 50000
I made sure to first open port 50000 on my machine for TCP for both inbound and outbound connections. (I even tried disabling the firewall completely.) Nothing seems to be working. I keep getting the error message:
No connection could be made because the target machine actively refused it.
I am using Windows 8. I would really appreciate some pointers on what else I might try.
Thanks in advance for your time.
EDIT
I hope I am not violating any of StackOverflow's posting policies by blogging about my progress here.
I have updated the code to the following:
let socket_CreateBindListen (sv_ : string) (pt_ : int) : Socket option =
let (he : IPHostEntry) = Dns.GetHostEntry(sv_)
let rsock, ipe =
he.AddressList
|> Seq.map (fun s ->
let (ipe2 : IPEndPoint) = new IPEndPoint (s, pt_)
let (rsock2 : Socket) = new Socket (ipe2.AddressFamily, SocketType.Stream, ProtocolType.Tcp)
try
rsock2.Connect ipe2
rsock2, ipe2
with
| _ ->
null, null)
|> Seq.find (fun (s, t) -> (s <> null) && (s.Connected))
try
rsock.Bind ipe
rsock.Listen sbl
printfn "%s now listening on port %d" sv_ pt_
Some (rsock)
with
| _ ->
printfn "Failed to connect to %s on port %d" sv_ pt_
None
Now I am getting the following error:
KeyNotFoundException was unhandled
An unhandled exception of type 'System.Collections.Generic.KeyNotFoundException' occurred in FSharp.Core.dll
I have looked extensively on Google and Bing, without any luck.
EDIT 2
As requested by Jack P., here is the output from netstat -a, as well as what happens when the binary is executed:
PS C:\Users\shredderroy> netstat -a
Active Connections
Proto Local Address Foreign Address State
TCP 0.0.0.0:80 SPEEDMACHINE:0 LISTENING
TCP 0.0.0.0:135 SPEEDMACHINE:0 LISTENING
TCP 0.0.0.0:445 SPEEDMACHINE:0 LISTENING
TCP 0.0.0.0:2179 SPEEDMACHINE:0 LISTENING
TCP 0.0.0.0:49152 SPEEDMACHINE:0 LISTENING
TCP 0.0.0.0:49153 SPEEDMACHINE:0 LISTENING
TCP 0.0.0.0:49154 SPEEDMACHINE:0 LISTENING
TCP 0.0.0.0:49155 SPEEDMACHINE:0 LISTENING
TCP 0.0.0.0:49156 SPEEDMACHINE:0 LISTENING
TCP 192.168.0.139:139 SPEEDMACHINE:0 LISTENING
TCP 192.168.0.139:49159 bn1wns2011708:https ESTABLISHED
TCP 192.168.0.139:49167 vc-in-f108:imaps ESTABLISHED
TCP 192.168.0.139:49171 vc-in-f108:imaps ESTABLISHED
TCP 192.168.0.139:49239 a23-67-250-112:http CLOSE_WAIT
TCP [::]:80 SPEEDMACHINE:0 LISTENING
TCP [::]:135 SPEEDMACHINE:0 LISTENING
TCP [::]:445 SPEEDMACHINE:0 LISTENING
TCP [::]:2179 SPEEDMACHINE:0 LISTENING
TCP [::]:49152 SPEEDMACHINE:0 LISTENING
TCP [::]:49153 SPEEDMACHINE:0 LISTENING
TCP [::]:49154 SPEEDMACHINE:0 LISTENING
TCP [::]:49155 SPEEDMACHINE:0 LISTENING
TCP [::]:49156 SPEEDMACHINE:0 LISTENING
UDP 0.0.0.0:500 *:*
UDP 0.0.0.0:4500 *:*
UDP 0.0.0.0:5355 *:*
UDP 127.0.0.1:53194 *:*
UDP 127.0.0.1:60316 *:*
UDP 127.0.0.1:61644 *:*
UDP 192.168.0.139:137 *:*
UDP 192.168.0.139:138 *:*
UDP [::]:500 *:*
UDP [::]:4500 *:*
UDP [::]:5355 *:*
UDP [fe80::b193:4f6:d053:6324%20]:546 *:*
PS C:\Users\shredderroy> cd "C:\Users\shredderroy\Documents\Visual Studio 2012\Projects\FSharp\SocketTests_Server\SocketTests_Server\bin\Debug
"
PS C:\Users\shredderroy\Documents\Visual Studio 2012\Projects\FSharp\SocketTests_Server\SocketTests_Server\bin\Debug> .\SocketTests_Server.exe
Unhandled Exception: System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it [::1]:50000
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Connect(EndPoint remoteEP)
at SocketTests_Server.TestModule_1.heo#22.Invoke(IPAddress s) in C:\Users\shredderroy\Documents\Visual Studio 2012\Projects\FSharp\SocketTests_Server\SocketTests_Server\TestModule_1.fs:line 25 at Microsoft.FSharp.Collections.SeqModule.TryFind[T](FSharpFunc`2 predicate, IEnumerable`1 source)
at SocketTests_Server.TestModule_1.socket_CreateBindListen_1(String sv_, Int32 pt_) in C:\Users\shredderroy\Documents\Visual Studio
2012\Projects\FSharp\SocketTests_Server\SocketTests_Server\TestModule_1.fs:line 20
at SocketTests_Server.Program.Main(String[] args) in C:\Users\shredderroy\Documents\Visual Studio 2012\Projects\FSharp\SocketTests_Server\SocketTests_Server\Program.fs:line 9
PS C:\Users\shredderroy\Documents\Visual Studio 2012\Projects\FSharp\SocketTests_Server\SocketTests_Server\bin\Debug>
I am going to keep trying. So far I have added my programme, SocketTests_Server.exe, to the list of allowed programmes in Windows Firewall, opened the relevant port for inbound and outbound connections, disabled the firewall completely--all to no avail.

Answer 1

I think what is happening is that you are connecting twice, one of the addresses connects fine. Your code then keeps looking through the remaining addresses and tries to connect again.
Your code is lacking the equivalent of break in the C# code.
Some possible solutions:
use a while loop instead of Seq.map
Use a reference variable inside the map
Compress all the code into Seq.find and remove the call to map (probably the most elegant)

Answer 2

I translated the code from the page you linked -- it compiles, though I haven't tried running it.
open System
open System.Text
open System.Net
open System.Net.Sockets
let connectSocket (server : string, port : int) : Socket option =
// Get host related information.
let hostEntry = Dns.GetHostEntry server
// Loop through the AddressList to obtain the supported AddressFamily. This is to avoid
// an exception that occurs when the host IP Address is not compatible with the address family
// (typical in the IPv6 case).
hostEntry.AddressList
|> Seq.tryPick (fun address ->
let ipe2 = IPEndPoint (address, port)
let rsock2 = new Socket (ipe2.AddressFamily, SocketType.Stream, ProtocolType.Tcp)
rsock2.Connect ipe2
if rsock2.Connected then
Some rsock2
else None)
// This method requests the home page content for the specified server.
let socketSendReceive (server : string, port : int) : string =
let request =
sprintf "GET / HTTP/1.1\r\nHost: %s\r\nConnection: Close\r\n\r\n" server
let bytesSent =
Encoding.ASCII.GetBytes request
let bytesReceived = Array.zeroCreate 256
// Create a socket connection with the specified server and port.
match connectSocket (server, port) with
| None ->
"Connection failed"
| Some s ->
// Send request to the server.
s.Send (bytesSent, Array.length bytesSent, SocketFlags.None)
|> ignore
// Receive the server home page content.
let mutable bytes = 0
let mutable page =
sprintf "Default HTML page on %s:\r\n" server
// The following will block until the page is transmitted.
while bytes > 0 do
bytes <- s.Receive (bytesReceived, Array.length bytesReceived, SocketFlags.None)
page <- page + Encoding.ASCII.GetString (bytesReceived, 0, bytes)
page
//
let main args =
let port = 80
let host =
if Array.isEmpty args then
// If no server name is passed as argument to this program,
// use the current host name as the default.
Dns.GetHostName ()
else
args.[0]
socketSendReceive (host, port)
|> Console.WriteLine
EDIT: I did a little digging, and "actively refused" is the key to that error message, according to: No connection could be made because the target machine actively refused it. In short, double-check that the server you're trying to connect to is set up properly; when the connection is actively refused, there's no firewall problem -- the server is actually rejecting your connection.
If you're absolutely certain the server is set up correctly, there's one last thing you could try. According to Socket Connection Is Actively Refused (MSDN Forums), you may need to use the IPAddress.NetworkToHostOrder Method to set the port value correctly for the IPEndPoint. In that case, just add this as the first line in my connectSocket function (above):
let port = IPAddress.NetworkToHostOrder port
EDIT 2: Looking at the netstat information you posted -- there's no server LISTENING on port 50000. If you're sure the server software is set up correctly, make sure it's using the port you want (and not just choosing a random port).

Answer 3

First, I would like to thank everyone, in particular, #Jack P. and #John Palmer, for reading my code and offering very good and instructive suggestions. Your guidance is greatly appreciated.
I have circumvented the problem described above by using the TcpListener and TcpClient classes instead. So I thought I would write the simple F# translations of this server function and this client function, which together implement the server and client. Hopefully, this sample code will save other beginners some time.
Server
let connectAndListen () : unit =
let (laddr : IPAddress) = IPAddress.Parse ("127.0.0.1")
let lpt = 32000
let (svr : TcpListener) = new TcpListener (laddr, lpt)
try
svr.Start ()
let (bta : byte[]) = Array.create 256 (byte (0))
while true do
printfn "Waiting for a connection..."
let (cl : TcpClient) = svr.AcceptTcpClient ()
printfn "Connected"
let (ns : NetworkStream) = cl.GetStream ()
let mutable (i : int) = ns.Read (bta, 0, (Array.length bta))
while i <> 0 do
let (dat : string) = System.Text.Encoding.ASCII.GetString (bta, 0, i)
printfn "Received: %s" dat
let (msg : byte[]) = System.Text.Encoding.ASCII.GetBytes (dat.ToUpper ())
ns.Write (msg, 0, (Array.length msg))
printfn "Sent: %s" (dat.ToUpper ())
i <- ns.Read (bta, 0, (Array.length bta))
cl.Close ()
with
| excp ->
printfn "%s" excp.Message
svr.Stop ()
Client
let connect (sv_ : string) (pt_ : int) (msg_ : string) : unit =
try
let cl = new TcpClient (sv_, pt_)
let (dat : byte[]) = System.Text.Encoding.ASCII.GetBytes msg_
let (st : NetworkStream) = cl.GetStream ()
st.Write (dat, 0, (Array.length dat))
printfn "Sent: %s" msg_
let (rdat : byte[]) = Array.create 256 (byte (0))
let (i : int) = st.Read (rdat, 0, (Array.length rdat))
let (rsp : string) = System.Text.Encoding.ASCII.GetString (rdat, 0, i)
printfn "Received: %s" rsp
st.Close ()
st.Dispose ()
with
| :? ArgumentNullException as excp ->
printfn "ArgumentNullException encountered: %s" excp.Message
| :? SocketException as excp ->
printfn "SocketException encountered: %s" excp.Message
printfn "Press ENTER to continue"
Console.ReadLine () |> ignore
Place the code in separate projects, compile and run them. They work on my machine.