File.Move System.IO.IOException: “No more connections can be made to this remote computer…”

Question

File.Move System.IO.IOException: "No more connections can be made to this remote computer at this time because there are already as many connections as the computer can accept".

I have a process running under SYS account. It is processing files on local HD and move them to a remote drive on a domain using impersonation.

Edit, added code sample:

The method bellow is called repeatedly (The Impersonation is a utility class I use for impersonation, this is irrelevant to the issue).

private void moveFileUsingImpersonation(string srcFilePath, string dstFilePath, string userName, string passWord)
        {
                WindowsImpersonationContext wic = null;
                // move it to destination 
                try
                {
                    wic = Impersonation.Impersonate(userName, passWord);
                    if (wic != null)
                    {
                        File.Move(srcFilePath, dstFilePath);
                    }
                    else
                    {
                        Console.WriteLine("moveFileUsingImpersonation, Failure to impersonate!");
                    }
                }
                catch(Exception ex)
                {
                    Console.WriteLine("moveFileUsingImpersonation, Exception={0}", ex.ToString());
                }
                finally
                {
                    Impersonation.UndoImpersonate(wic);
                }
            }

Edit, added code sample.

When the process is running on XP machine and the remote Drive is on either XP or Win7 machine the call to File.Move works just fine and move the required files. However when the process is running on Win7 and remote Drive is on Win7 machine the mentioned exception is thrown after 20 files have been moved.

I've also tried to call the win32 API MoveFileEx with the MOVEFILE_REPLACE_EXISTING & MOVEFILE_COPY_ALLOWED & MOVEFILE_WRITE_THROUGH flags, with the same result - ERROR_REQ_NOT_ACCEP 71 (0x47).

It seems that the underlying connection made by the call to File.Move isn't closed properly on Win7.

Is there a way to overcome this?

What am I missing here?

Thanks, Ilan

Answer 1

Based on your code, you're probably copying using a UNC path. I've alway had issues doing this, and I've learned it's best to just map and then disconnect drives in code as needed. It saves me from having to deal with permissions issues, and also issues like the one you're describing.

We have a class that handles this for us. We've been using it for over 5 years with no issues, including on Win7 machines on both the code and remote side. Hoefully it will work for you as well.

public static class NetworkDrives
    {
        public static bool  MapDrive(string DriveLetter, string Path, string Username, string Password)
        {

            bool ReturnValue = false;

            if(System.IO.Directory.Exists(DriveLetter + ":\\"))
            {
                DisconnectDrive(DriveLetter);
            }
            System.Diagnostics.Process p = new System.Diagnostics.Process();
            p.StartInfo.UseShellExecute = false;
            p.StartInfo.CreateNoWindow = true;
            p.StartInfo.RedirectStandardError = true;
            p.StartInfo.RedirectStandardOutput = true;

            p.StartInfo.FileName = "net.exe";
            p.StartInfo.Arguments = " use " + DriveLetter + ": " + '"' + Path + '"' + " " + Password + " /user:" + Username;
            p.Start();
            p.WaitForExit();

            string ErrorMessage = p.StandardError.ReadToEnd();
            string OuputMessage = p.StandardOutput.ReadToEnd();
            if (ErrorMessage.Length > 0)
            {
                throw new Exception("Error:" + ErrorMessage);
            }
            else
            {
                ReturnValue = true;
            }
            return ReturnValue;
        }
        public static bool DisconnectDrive(string DriveLetter)
        {
            bool ReturnValue = false;
            System.Diagnostics.Process p = new System.Diagnostics.Process();
            p.StartInfo.UseShellExecute = false;
            p.StartInfo.CreateNoWindow = true;
            p.StartInfo.RedirectStandardError = true;
            p.StartInfo.RedirectStandardOutput = true;

            p.StartInfo.FileName = "net.exe";
            p.StartInfo.Arguments = " use " + DriveLetter + ": /DELETE";
            p.Start();
            p.WaitForExit();

            string ErrorMessage = p.StandardError.ReadToEnd();
            string OuputMessage = p.StandardOutput.ReadToEnd();
            if (ErrorMessage.Length > 0)
            {
                throw new Exception("Error:" + ErrorMessage);
            }
            else
            {
                ReturnValue = true;
            }
            return ReturnValue;
        }

    }