Checking remote TCP connections

I have a computer that we will call A, and I want other computers (B, C, D, ...) to send data to a specific TCP port on A. I have that working, but the problem I am having is that I want only one computer at a time to be able to send the data to A.
For instance, if B is already communicating with A, I want C to throw an error. I have ran some simple tests and it appears that B and C can write to the same port on A at the same time. The port seems to create a buffer that collects the data from both computers.
Is there a way to configure the port to be a single writer like you can in shared variables? (By the way, i have tried the shared variable route but wasn't liking the communication speed.)
Or is there a way when I try to open a connection from B, C, ... that it checks to see if A's port is already connected to another computer?
I hope this A, B, C description isn't too confusing.

Hi ejw,
attached you will find an example of a server which can only have one connection simultaneously.
Hope it helps.
Mike
Message Edited by MikeS81 on 06-10-2008 09:21 PM
Attachments:
client.PNG ‏4 KB
server.PNG ‏8 KB

Similar Messages

Can I check remote address connecting to a ServerSocket before accepting?

I have a ServerSocket for which I'd like to implement an IP filter, using an allow or deny list to control which IP addresses can connect. After accepting the connection, I check the remote address on the Socket that is created, and apply the filter. However, if I close the connection to a denied address, the client sees that the connection was accpeted, but then it throws a SocketException when it tries to write to it.
That accomplishes the purpose of the filter, but it doesn't seem like good behavior from the client's perspective. I'd like to implement a ServerSocket that doesn't even accept the connection if the remote address is not permitted. Is there any way to do that?

Why not write a connection accepted/refused message
to the client and then carry on (or close the
socket/streams at both ends)?I'm not sure I understand your suggestion. When ServerSocket.accept() returns by providing a Socket object, that is the first time the server code can determine the IP address of the client and apply an IP filter. However, the connection has already been established at this point, so it's not possible to make an accept/refuse decision for the connection based on the client IP address. By the time the server code sees the IP address, the connection has already been accepted, and the only recourse is to close the connection from the server (by calling close() on the Socket object that was returned), and the client will then throw an exception with the message saying that the software closed the connection.
Legitimate users trying to connect may interpret this as a software problem, if they don't know any better. Intruders will discover from this behavior that the port is open through the firewall, and may conclude that IP filtering is being applied, and if they have some idea of what IP addresses are allowed, they could easily spoof them. Or they could keep trying, hoping to catch the server when the IP filtering is turned off.
It would be better to mimic the filtering behavior of a firewall, whereby the connection is not established. Then the client would report that it could not establish the connection, and the user would be more likely to look into whether the port is open or IP filtering is occurring, rather than thinking there is a software problem. And the intruder would conclude that the port is not open and go somewhere else.
I would need a different implementation of ServerSocket to do this. I checked jakarta commons net, but that only provides client side utilities. I'm currently untangling the source code of java.net.ServerSocket to see how difficult it will be to override the accept() method to provide filtering behavior. This seems like a useful thing, and I thought perhaps someone had already done so. Or perhaps someone can tell me why this is not a good idea.
Message was edited by:
MidnightJava

TCP Connection lost in between TCP read operation

Hi all,
Is there any method to check whether TCP connection is lost ? Actually in my program server may need to read the data for 44 minutes & i want to know that while reading say after 20 minutes connection is lost for unknown reasons. In that condition i should make sure that connection is estalished / lost. If in between this happens than i should inform user the same.
Any implementation of this type.
Kudos are always welcome if you got solution to some extent.
I need my difficulties because they are necessary to enjoy my success.
--Ranjeet

Ranjeet_Singh wrote:
Hi all,
Is there any method to check whether TCP connection is lost ? Actually in my program server may need to read the data for 44 minutes & i want to know that while reading say after 20 minutes connection is lost for unknown reasons. In that condition i should make sure that connection is estalished / lost. If in between this happens than i should inform user the same.
Any implementation of this type.
There is no direct method other than the results of transmitting/receiving data. If you get an error 66 that would indicate that the connection has been closed by the other side. However, you will not get this until you try to send/receive data. If you are receiving data continuously you can looki for a timeout error (error 56). You may also get an error 52. The end result is that you need to check the error codes and then take whatever action you deem necessary.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot

TCP connectivity of subnet error : pre installation check oracle 11.2 RAC

Hi,
I am trying to setup RAC 11.2 on Centos 5.7.
When I run the preinstallation check, I am getting this error:
Check: Node connectivity of subnet "192.168.210.0"
Source Destination Connected?
rac2[192.168.210.102] rac1[192.168.210.101] yes
Result: Node connectivity passed for subnet "192.168.210.0" with node(s) rac2,rac1
Check: TCP connectivity of subnet "192.168.210.0"
Source Destination Connected?
falca:192.168.100.218 rac2:192.168.210.102 failed
ERROR:
PRVF-7617 : Node connectivity between "falca : 192.168.100.218" and "rac2 : 192.168.210.102" failed
falca:192.168.100.218 rac1:192.168.210.101 passed
Result: TCP connectivity check failed for subnet "192.168.210.0"
Check: Node connectivity of subnet "192.168.100.0"
Source Destination Connected?
rac2[192.168.100.219] rac1[192.168.100.218] yes
Result: Node connectivity passed for subnet "192.168.100.0" with node(s) rac2,rac1
Check: TCP connectivity of subnet "192.168.100.0"
Source Destination Connected?
falca:192.168.100.218 rac2:192.168.100.219 failed
ERROR:
PRVF-7617 : Node connectivity between "falca : 192.168.100.218" and "rac2 : 192.168.100.219" failed
falca:192.168.100.218 rac1:192.168.100.218 failed
ERROR:
PRVF-7617 : Node connectivity between "falca : 192.168.100.218" and "rac1 : 192.168.100.218" failed
Result: TCP connectivity check failed for subnet "192.168.100.0"
There is some problem between the physical IP and the private IP connection.
However I am able to ping successfully and also SSH successfully between the physical IP and the private IP.
What could be the problem?

hello, i am have problems installa oracle RAC 11.2.0.3 Helpppppppppppppppp
Here are the 2 Virtual machine details:
VM used: Oracle Virtual box 4.2.8
Cluster Version: 11g R2 (11.2.0.3)
Windows version: Windows 2008 Server R2
No of node: 2
Node details:
Node 1 hostname: w2008-112-rac1
Public ip (eth0): 192.168.0.151
Subnet mask: 255.255.255.0
Default gateway: 192.168.0.1
DNS: 192.168.0.4
Private ip (eth1): 192.168.1.151
Subnet mask: 255.255.255.0
Default gateway: none
DNS: none
Node 2 hostname: w2008-112-rac2
Public ip (eth0): 192.168.0.152
Subnet mask: 255.255.255.0
Default gateway: 192.168.0.1
DNS: 192.168.0.4
Private ip (eth1): 192.168.1.152
Subnet mask: 255.255.255.0
Default gateway: none
DNS: none
file hosts
127.0.0.1 localhost.localdomain localhost
# Public
192.168.0.151 w2008-112-rac1.localdomain w2008-112-rac1
192.168.0.152 w2008-112-rac2.localdomain w2008-112-rac2
#Private
192.168.1.151 w2008-112-rac1-priv.localdomain w2008-112-rac1-priv
192.168.1.152 w2008-112-rac2-priv.localdomain w2008-112-rac2-priv
#Virtual
192.168.0.153 w2008-112-rac1-vip.localdomain w2008-112-rac1-vip
192.168.0.154 w2008-112-rac2-vip.localdomain w2008-112-rac2-vip
#SCAN (192.168.0.155 - 192.168.0.157 in DNS)
192.168.0.155 w2008-112-scan.localdomain w2008-112-scan
192.168.0.156 w2008-112-scan.localdomain w2008-112-scan
192.168.0.157 w2008-112-scan.localdomain w2008-112-scan
Error **************
ERROR: PRVF-7617 : Node connectivity between "w2008-112-rac1: 192.168.0.151" and "w2008-112-rac2: 192.168.0.152" TCP connectivity check failed for subnet "192.168.0.0"
help Plis ......

Coherence Extend remote address port in TCP Connection

Hi,
From the log below, I see remote address port is picked some random port(48552). (currently i disabled the firewall), If i enable the firewall it could be an issue, is there any way i can specify the remote ports that tcp connection use?
2011-02-24 13:18:18.076/1280.207 Oracle Coherence GE 3.6.0.1 <D6> (thread=Proxy:ExtendTcpProxyService:TcpAcceptor, member=13): Opened: TcpConnection(Id=0x0000012E56A3CA1B0A1F96B688F7EEBCEDA2AA9397203393CF480379B3963D86, Open=true, LocalAddress=10.31.150.182:9099, RemoteAddress=10.31.150.182:48552)
One more question,
I have two proxy servers, is it possible to configure the client to make two connection (redundant) one for first proxy and another for second proxy. is it make sense?
Thanks
Prab
Edited by: 833796 on Feb 24, 2011 2:35 AM

Hi Prab
The random port is what normally is called an ephemeral port for the client and is usually not a problem for firewalls since this is expected behavior. If you want to control the client port you can do this by adding the <local-address> to the tcp-initiator element.
As for the second question, it doesn't quite work to do as you suggest. The proxy contains state for the client, as this is not replicable between the proxies one cannot continue where the other one left off.
Thanks
/Charlie

TCP connectivity check failed for subnet

hi
im trying to add a node to my 11.2 grid infrastructure and the cluster verification is returning error
Check: TCP connectivity of subnet "152.15.123.0"
Source Destination Connected?
inode2:127.0.0.1 inode2:152.15.123.4 failed
Result: TCP connectivity check failed for subnet "152.15.123.0"
this happens when i run cluvfy with pre nodeadd option, there is no other failure ...
any idea what it could be ?

Hello Buddy,
Please note that inode2:127.0.0.1 is using loopback IP, please check your network configuration and retry the cluvfy operation.
Cheers,
Rodrigo Mufalani
www.mufalani.com.br/blog

RAC - Cluvfy - TCP connectivity check failed for subnet

Hi ...this is Oracle RAC 10.2.0.4.0 .. has anyone witnessed this check failure or is able to comment on how I should debug the same
./runcluvfy.sh stage -post hwos -n all -verbose
Check: TCP connectivity of subnet "172.30.182.0"
Source Destination Connected?
sekiazu0230:172.30.182.67 sekiazu0231:172.30.182.68 failed
sekiazu0230:172.30.182.67 sekiazu0231:172.30.182.68 failed
Result: TCP connectivity check failed for subnet "172.30.182.0"
Interface information for node "sekiazu0230"
Name IP Address Subnet Gateway Def. Gateway HW Address MTU
en0 172.30.182.67 172.30.182.0 172.30.182.67 172.30.182.1 1E:40:3D:1C:96:02 1500
en0 172.30.182.67 172.30.182.0 172.30.182.67 172.30.182.1 1E:40:3D:1C:96:02 1500 ===> Duplicated ?
en1 172.30.190.48 172.30.190.0 172.30.190.48 172.30.182.1 1E:40:3D:1C:96:03 1500
en2 10.252.34.9 10.252.34.0 10.252.34.9 172.30.182.1 1E:40:3D:1C:96:04 65390
Thank you for all feedback
Steve

Hello Buddy,
Please note that inode2:127.0.0.1 is using loopback IP, please check your network configuration and retry the cluvfy operation.
Cheers,
Rodrigo Mufalani
www.mufalani.com.br/blog

ACE connection limit and remote TCP security scans

We are currently running remote TCP security scans on our networks and are running into a major problem where when the scans are taking place the ACE connection resource usage sky rockets and easily reaches the maximum 4 million connections. This means that anyone can run a simple TCP scan and take down our ACE by maxing the connection limit. We have the following parameter-map applied to all of our policies but it does not help to clear the connection count on the ACE in a reasonable amount of time. parameter-map type connection CONNECTION_TIMEOUT set timeout inactivity 300 set tcp timeout half-closed 60 I should note that we do have normalization turned off because it causes way more problems then it's worth (no resolution with TAC). Does anyone have an tips on how to accommodate security scan's on networks behind the ACE while not saturating the connection count limit?

For vips, this particular context only has one class C applied to a class-map. Not all IP's are in use but regardless the ACE creates connections for those as well. I've set the timeout inactivity to 120 seconds and I still see connections from the remote scanning host idling well over 45mins for connections destined to the vip's. Is turning on normalization my only option? I know there are others who have turned off normalization due to performance and connectivity issues so there must be other ways around this. Thanks for your help.

Remote Desktop Connection

I'm running bootcamp Windows 8 on a MacBook Pro and a MacMini (on home network).
I have them set up for remote access. At home on the same network, I can remote desktop to the MacMini using the local IP address with no problems.
I then wanted to access it from an external network so I enabled the default 3389 port in my firewall settings and set up this port to my MacMini in my router settings. I reserved the IP address for the MacMini as well.
I was able to successfully connect from an external network at least once but once my external IP address changed, I was no longer able to get it to work after updating the IP address. The computer is on because I can access it using TeamViewer and I use
that to check the current IP address of the MacMini when I'm trying to connect.
To get around the dynamic IP problem, I signed up for a dyndns account and set up a host name. I can use a port check and the host name ***.dyn-o-saur.com resolves to the correct IP address (i.e., the whatismyip.com result on the MacMini).
I have tried changing the port to 8888 in case TeamViewer or some other application was using 3389 but that hasn't fixed the problem either. I've checked the port (using http://www.t1shopper.com/tools/port-scan/) and I get this message:
***.dyn-o-saur.com is responding on port 8888 (ddi-tcp-1).
I have the dynUpdater v5.0.1 installed on both computers and it says the host is inactive (however since the hostname is resolving properly I assume this means the app is not working but it shouldn't be affecting my ability to connect?).
Some help please?

Hi,
Firstly, we need to refer to this article and configure the settings.
Allow Remote Desktop connections from outside your home network
http://windows.microsoft.com/en-us/windows7/allow-remote-desktop-connections-from-outside-your-home-network
From you description, I think you have done this part. However, please keep to use port 3389 and make sure that you can RDP to your Windows 8 via the
Public IP address from Internet.
Then, as you have dynamic public IP address, we need some way to track the changes of your public IP address. Yes, dyndns is one of the methods, you need to make sure that it
can resolve the host name you registered to the correct Public IP address so that you can always RDP you Windows 8 via host name when you outside your home.
If you need assistance about dyndns, please contact their support.
Thanks.
Jeremy Wu
TechNet Community Support

Remote desktop connection problem windows 8

Hi everybody,
I hope you can help us. We run a software package that uses a remote desktop connection. When the program is minimised for more than a couple of minutes, the connection disconnects and takes a while to reconnect. We've been in touch with the guys that run
the program and they've said that there's no problem on their end and that it must be on our end. It's happening with all three computers at one location and it's not happening with our two computers in our other location.
I've been in touch with the online support guys in microsoft and they couldn't help. So I'm wondering if any of you can help us (in laymans terms please!).
All our computers run Windows 8.
Thanks in advance.

Hi,
Thank you for your posting in Windows Server Forum.
Yes, you can check with 2 different settings. 1) By Collection properties (Server 2012\R2) and RDP-Tcp connection under Remote Desktop Service Manager (Server 2008 R2). 2) The other setting is related to GPO (Set time
limit for active but idle Remote Desktop Services sessions) as following path.
Computer Configuration\Policies\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Session Time Limits
User Configuration\Policies\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Session Time Limits
You can check below link (Configuration 1) for more information.
[Forum FAQ] Restrict number of Active Sessions in RDS 2012 and 2012 R2
http://social.technet.microsoft.com/Forums/en-US/00c2252b-8ec0-489f-8da2-07a434a9b5a2/forum-faq-restrict-number-of-active-sessions-in-rds-2012-and-2012-r2?forum=winserverTS
Hope it helps!
Thanks.
Dharmesh Solanki

Remote Desktop Connection with WRT54G from Novice

Well, I’m usually pretty good at using Google and forums to eventually figure out how to fix my problem but this one absolutely has me stumped and I’m hoping someone out there has an answer for me. For the record, I have probably a beginner/intermediate knowledge of computers so if you know the answer to my problem, try to explain it simply! ****TO ANYONE WHO TAKES THE TIME TO READ THIS THING AND CAN OFFER SOME ADVICE-THANK YOU!!!!***
THE PROBLEM
I would like to be able to use Remote Desktop to log into either of my home computers from basically any computer on the internet.
THE SETUP
I have two computers, whose names are LAPTOP and DESKTOP that are both running Windows Vista Ultimate. Both of the computers are connected to a Linksys WRt54G Router ; one wired, the other wirelessly. The Linksys router is then connected to a Westell DSL Modem that connects to AT&T’s internet service.
SETTINGS
My DSL service only provides me with a dynamic IP address so I signed up with no-ip.com. Through that site, I bought a domain name and downloaded their small program that runs in the background of my desktop computer. The program checks what my IP address is every couple of seconds and if it changes, it notifies their server so that anyone who types in my domain name is directed to the new IP address.
ROUTER (Firmware 4.20.6)
Basic Setup Page: The Router Name is just the model number, the Server Name is my DSL provider and the Domain Name is the name I chose and registered with No-IP.com. (www.mydomainname.com, for example.) DHCP Server is ENABLED. DDNS Service is DISABLED. Under Advanced Routing, it is set in GATEWAY mode.
Security Page: Firewall Protection is ENABLED. Block Anonymous Internet Requests is NOT checked. Filter Multicast, Filter Internet NAT Redirection and Filter IDENT ARE checked.
Applications and Gaming Page: I chose two port numbers, one for each computer that I want to connect to. On the first line, I have Application: RDP, Port Range: 49200 to 49200, Protocol: Both, IP Address (The IP address of the computer I want to connect to) and the Enable box IS checked. [I did the same thing with the second line for the other computer, but with a different port number and that computer’s IP address)
Administration Page: Access Server is HTTP, Wireless Access Web is ENABLED, Remote Management is ENABLED through Port 8080, and UPnP is ENABLED.
WINDOWS VISTA SETTINGS
First, I went to the Remote Desktop Settings of the target computer and ENABLED Remote Desktop Connection and allowed computers running any version of Windows. I also confirmed that the box labeled “Allow This Computer To Be Controlled Remotely” WAS checked. I then made sure that I had a user name, it had a password associated and that it had Administrator priveledges. I went back to the Remote Connections screen and added the user name as being allowed to connect. (I think this is redundant since it’s both the owner of the computer and has Administrator Status.)
Next, per Randomly Googled Internet Advice, I went into the registry and changed the port number that Remote Desktop listens for incoming connections to Port 49200 to match the router settings. [Registry Entry that I modified was: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp]
Finally, I went to the Windows Firewall and Added (opened) port 49200 for use as a Remote Connection. I kept the protocol as TCP and confirmed the scope was set for Any Computer.
CURRENT STATUS
If I go to Explorer and enter my IP address with a colon and the specify port 8080, I can get the login screen for the router. Same thing happens if I just enter my domain name and port 8080. However, if I switch the 8080 port and use one of the ports I chose (49200), it cannot connect, either using the Public IP address or the domain name. (I’m trying to connect using a wireless card and not connected to my local network so I know it’s the same as if I was anywhere else.)
I’m not sure why it won’t let me connect; it feels like the router will not allow the connection to pass through it to the port I’m asking it to forward to. I’m guessing someone out there who took the time to read it is shaking their head at all the information I provided and knows the one dumb thing I missed!
Thanks again!

I'm attempting to do the same thing with my home network. the only differences are that i have cable internet from comcast and i'm running vista business. my router is the wrt54gs. i'm assuming that the web page is similar for adjustmants. To be honest i cannot figure out how to do a remote destop too. so i went to www.logmein.com and installed the program. once installed to to every computer you want to have access too and log into the website. then click on the add computer icom. full control app sharing etc... even better when you connect you have the option to deactivate the local host mouse and screen to prevent anyone seeing what your doing.
If you resolve the router issue would you let me know. plz thanks
Forest

Remote Desktop Connection Client 9.3.9600 unable to connect to Server 2012 RDS via Gateway

Hi,
I have a Windows Sever 2012 R2 RDS environment with two Gateways servers configured in high availability mode (RD Web Access, RD Gateway, RD Connection Broker roles installed) and four Windows Server 2012 R2 RDS Session Hosts. The servers are all running
the most recent public server updates. With this configuration I when connecting externally using a Windows 7 computer with the older Remote Desktop Connection client (6.1.7601) I am able to connect without any problems however when I try connecting with a
newer client from a computer running Windows 8.1 and the 9.3.9600 client I am unable to connect.
At the moment a NAT rule is configured to pass 80/443 traffic to only one of the RDS gateway servers, I've removed our load balancer from the configuration for the moment to reduce the complexity.
No error is generated by the client when it tries to connect it just stops trying to connect after a while.
On the Gateways servers event logs for
Things I have looked into so far.
- I've double and triple checked the RDS configuration and checked it against one of my other clients configurations that is working and they are identical.
- Connecting from an older client version works fine.
I'm not sure what else can be checked does anyone have any ideas?

Hi,
1. What entries are you seeing in the RD Gateway's log? Event Viewer\ Applications and Services Logs\ Microsoft\ Windows\ TerminalServices-Gateway
2. How come you are not forwarding UDP port 3391 in addition to TCP port 443? It should work without UDP, but you will not have UDP support which is one of the benefits of RDP 8.0/8.1.
3. Are there any non-default group policy settings being applied to the servers and/or client PCs? To be clear, I'm asking if any changes have been made to the default local and domain security policies, group policy objects, new GPOs that may have
been added, etc., that are applicable to the servers and or client PCs.
-TP

Can I use Remote Desktop Connection (windows server 2008) even if no user is logged in?

I'm configuring a Server, running Windows Server 2008, to be accessed remotely. Suppose no user is logged in in the server (if it was just turned
on, for instance). Can I use the "Remote Desktop Connection" feature to log in remotely in this case? Or is it always necessary to have a user locally logged in, to remotely log in to one of the users available?

If its a fresh installation, RDM might not work at first.
1. You need to check firewall and allow Remote Desktop. To be specific, communication to port 3389 TCP
2. Right click My Computer --> Properties --> Remote tab
Enable Remote Desktop
Allow connections to this computer
Click users and grant the permissions for the users. By default, Administrators do have the permission. An also, the users who are members of the 'Remote Desktop Users' security group also have the permission

Remote Desktop Connection Drops when opening a large file or Transferring a large file

I am running a Dell R720 Windows 2008 R2 Server. When I open a Large PDF or transfer a large file to the server, the server drops the remote desktop connection. I do not see any errors and no events are reported. I can access the server via
iDRAC 7 enterprise and the server is still up and functioning properly; however, the remote desktop connection can only be restored after the server is rebooted. I have read the following article below do not see any conflicts.
http://support.microsoft.com/kb/2477133/en-us
That said, the issue happens when:
1. opening a large PDF
2. Using a UNC path to transfer a large file
3. Using Hyper-V to import a .VHD (another large file)
Any help is appreciated - Thanks in advance

Hi,
Thank you for posting in Windows Server Forum.
Does this issue facing for single user or multiple users?
Have you tried on other system? IS it, facing same issue.
From description it seems network issue, please check whether there is any drop for network connection or it works on low bandwidth. You need to see there is no loss from bandwidth perspective. There are other certain reason which can drop the connection or
performance as remote desktop works on many different points.
For try you can autotune disable and check with following command.
netsh interface tcp set global autotuning=disabled
To renable follow beneath command
netsh interface tcp set global autotuninglevel=normal
When you are remote desktop to the remote server, please set the connection speed accordingly to optimize performance and might it will resolve your case of dropping connection.
More information.
Announcing the Remote Desktop Protocol Performance Improvements in Windows Server 2008 R2 and Windows 7 white paper
http://blogs.msdn.com/b/rds/archive/2010/02/05/announcing-the-remote-desktop-protocol-performance-improvements-in-windows-server-2008-r2-and-windows-7-white-paper.aspx
Hope it helps!
Thanks.
Dharmesh Solanki
TechNet Community Support

Remote desktop connects, black screen, disconnects after a few seconds

I have several servers running Windows Server 2012 R2. These servers are used for testing, and are members of a domain which has two DCs, each of which are running DNS Server.
Yesterday I noticed one of the servers was having an issue with its remote desktop connection. If I try remoting into this machine, it connects to a black screen, sits there for 2-3 seconds and then promptly disconnects. No error message is given. I tried
this from a couple different Windows 7 machines, and got the same result. I tried from my wife's iMac, which runs Jump Desktop, and too was met with the same result.
I can, however, remote into this machine via RDP from my work-issued laptop, which is running Windows 8. However, I cannot remote into the problem machine via Remote Desktop Connection from one of the 2012 R2 servers--I am met with the same result as the
other machines: connect, black screen for 2-3 seconds, disconnect without error.
I can remote into all of the other 2012 R2 servers without issue from any machine, including the iMac. I am experiencing this problem on one server only.
Since it is a test server, I reinstalled Windows from scratch this morning. This meant formatting the SSD and wiping everything out. I reinstalled the drivers, joined the server back to the domain and installed all of the updates available from Windows Update.
And rebooted. And yet, the problem persists!
I tried troubleshooting the "usual suspects," like turning off Windows Firewall, disabling antivirus software (currently none installed), disabling IPv6, setting a static IP instead of using DHCP, etc. I did notice the network adapter said it was
on a Network, not a Domain Network. I corrected DNS settings, and the network reidentified itself as being on the ParietalBone.net network. And yet, the problem persists. Remote Desktop to this server still yields a black screen for 2-3 seconds, followed by
a disconnect--EXCEPT from the aforementioned Windows 8 machine.
I looked in the TerminalServices-LocalSessionManager log on the offending server, and there are no errors. I only see repeated entries that say "Session X has been disconnected, reason code 12," where X is 1 or 2. On a couple occasions, the reason
code is 11. But I don't see any errors indicating a breakdown in security negotiation.
Without any robust logs or debug details, I'm at a loss of where to look for a solution.

I am cautiously optimistic that this may have been resolved.
The network card in the computer was only a 10/100 built-in card, so I replaced it with a 1Gbps card. Interestingly, this did NOT resolve the issue. I ran netsh to check on the state of the chimney offload, but it was already disabled.
In the network card properties, I changed the link speed and duplex from automatic to 1Gbps full, re-ran "netsh int tcp set global chimney=disabled" and rebooted. The problem persisted.
And so I went to the network card properties and set IPv4 Checksum Offload, Large Send Offload (three of these -- IPv4, v2 IPv4 and v2IPv6) and TCP Checksum Offload (IPv4 and IPv6) to Disabled. Jumbo Frames were also disabled. I rebooted again.
After the subsequent reboot, I was able to connect to this Server from machines that previously gave me difficulty. The only machine I haven't been able to test today (I'm in the office) is my wife's iMac, which is at home. However, I was able to bring this
server up via Jump Desktop on my iPad, so I'm suspecting that perhaps one of the offload options was to blame. I'm not sure why this would allow me to connect from some machines but not others. And as noted above, I have many other machines running Server
2012 R2 and they are NOT experiencing this problem. And I've not done any tinkering with network settings on any of them, so their chimney and offload settings are all in the default configuration.
Regarding the other items -- NIC team, virtual machine, etc. -- there was no NIC team, no SRIOV and no RDMA involved.
I had to turn IPv6 off on this machine, and only on this machine, because having it enabled was causing a lot more problems. DNS registration would keep failing, it couldn't pull Group Policy, it couldn't get time sync with the DC, etc. The servers are all
set up with static IPv4 addresses. The router supports IPv6 but I'm not actually using it, so disabling IPv6 wasn't a concern to me.

Checking remote TCP connections

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