Fix Run Server Error 0X00000955 on Windows Server

When This Error Shows Up

You're sitting at a Windows Server 2019 or 2022 machine. You try to run a script or a scheduled task that talks to another server—maybe a Run server for a legacy app or a custom service. And boom. You get this: "An error occurred when communicating with a Run server. The exact error code is: 0X00000955."

I've seen this happen most often with older line-of-business apps that use a central Run server to push jobs out to other servers. The app tries to connect, but the connection fails. The error code maps to NERR_ErrCommRunSrv, which just means "can't talk to the Run server."

What Causes It

The root cause is almost always one of three things:

• Network issue: The client server can't reach the Run server over the network. Maybe a firewall is blocking the port, or DNS is pointing to the wrong IP.
• Service account problem: The service or scheduled task running on the client doesn't have the right permissions on the Run server. Or the account is locked out or expired.
• SMB or RPC problem: The Run server might be using SMB (port 445) or RPC (port 135) for communication. If those ports are blocked or the SMB service isn't running, the connection fails.

In my experience, 9 times out of 10 it's a firewall or DNS issue. But I've also seen it when someone changed a service account password and forgot to update it in the task scheduler.

How to Fix It

Follow these steps in order. Test after each step to see if the error goes away.

Step 1: Test Basic Network Connectivity

1. Open Command Prompt as administrator on the client server.
2. Run ping [RunServerIP] — replace [RunServerIP] with the actual IP address of the Run server. You should see replies. If not, skip to the firewall check below.
3. Run ping [RunServerName] — use the hostname. If that fails but the IP works, you have a DNS problem. Check DNS settings in network adapter properties.

Step 2: Check the Firewall

1. On the Run server, open Windows Defender Firewall with Advanced Security.
2. Check inbound rules. Look for rules that might be blocking ports 135 (RPC), 445 (SMB), or any custom port your app uses.
3. If you're not sure which port the Run server uses, check your app's documentation. Or run netstat -an on the Run server to see listening ports.
4. Create a new inbound rule to allow traffic on that port if it's blocked.
5. On the client server, make sure outbound rules don't block the same port.

After you change a firewall rule, wait about 10 seconds. Then run telnet [RunServerIP] [port] to test the connection. If it connects, the firewall was the problem.

Step 3: Verify Service Account Permissions

1. On the client server, open Task Scheduler (or Services.msc if it's a service).
2. Find the task or service that's failing. Right-click and pick Properties.
3. Go to the "General" tab. Note which account is running the task (like "NT AUTHORITY\SYSTEM" or a domain account).
4. On the Run server, give that account the necessary permissions. Usually that means adding it to the local Users group or a custom group for your app.
5. If the account uses a password, make sure it's still valid. You can test by logging into the client server with that account and trying to access a share on the Run server.

Step 4: Check SMB and RPC Services

1. On both servers, open Services.msc.
2. Make sure "Server" service is running (it handles SMB).
3. Make sure "Remote Procedure Call (RPC)" service is running.
4. If either is stopped, right-click and start it. Set startup type to Automatic.

Step 5: Restart the Run Server Service

1. On the Run server, open Services.msc.
2. Find the service that provides the Run server functionality (might be named something like "Run Server Service" or your app's service).
3. Right-click and select Restart.

Sometimes the service just gets stuck. Restarting it clears the cobwebs.

What If It Still Fails?

If you've done all the steps above and the error still appears, check these:

• Event Viewer logs: On both servers, open Event Viewer and look under Windows Logs > System. Filter for Error or Warning events around the time the error occurred. They might point to a specific driver or service failure.
• Antivirus or security software: Some security suites block inter-server communication. Temporarily disable the antivirus on both servers and test. If the error goes away, add an exception for your app's port or process.
• Application logs: Check the Run server's application logs (in Event Viewer under Applications and Services Logs). The app might log a more specific error message.
• Network trace: Run a packet capture with Wireshark or netsh trace on the client server. Filter for traffic to the Run server's IP. You'll see exactly where the connection fails—at the TCP handshake, at the SMB negotiation, or later.

One last thing: if this is a custom app, talk to the developer. They might know exactly which port or protocol the Run server uses. I've wasted hours guessing ports before I just called the vendor.

Good luck. Error 0X00000955 is annoying, but it's fixable.