WSASERVICE_NOT_FOUND 0X0000277C fix for Windows Server

What's actually happening here

Error 0X0000277C with the message WSASERVICE_NOT_FOUND — No such service is known means Windows Sockets (Winsock) couldn't locate a required network service during WSAStartup(). Under the hood, WSA calls into the Service Name Resolution Provider (SNRP) to resolve a service name — like _ldap._tcp.domain.com. If the DNS client service is dead, or the registry path for service providers is hosed, WSA gives up and returns this error. I see this most often on Windows Server 2019 and 2022 after a failed update or when someone stops the DNS Client service to "save resources."

Quick fix — 30 seconds

Restart the DNS Client service

The single most common cause: the DNS Client service (dnscache) is stopped or hung. WSA depends on it for name resolution, even for local service lookups.

Open a command prompt as Administrator.
Run:
```
net start dnscache
```
If it's already running, restart it:
```
net stop dnscache && net start dnscache
```
Try your app again. If it works, you're done.

Why this works: WSA's service resolution queries the registry under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters, but it actually uses the DNS Client service to route those queries. If dnscache is off, any getaddrinfo() or WSALookupServiceBegin() call with a service name fails immediately with 0X0000277C. Starting the service restores that routing.

Moderate fix — 5 minutes

Check service dependencies and Winsock catalog

If the quick fix didn't stick, or the error comes back after a reboot, something deeper is wrong. Two things to check:

1. Verify DNS Client service dependencies

The DNS Client service depends on the NSI (Network Store Interface) service and TCP/IP Protocol Driver. If NSI is stopped, dnscache won't start correctly.

Run services.msc.
Find DNS Client, right-click, choose Properties.
Click the Dependencies tab. Make sure NSI and Tcpip are running. If NSI is stopped, start it:
```
net start nsi
```
Then start or restart dnscache.

2. Reset Winsock

A corrupted Winsock catalog can cause WSA to fail when registering or querying service providers. This is rare but happens after malware removal or bad network drivers.

Run as Administrator:
```
netsh winsock reset catalog
```
Reboot.

Why this works: The Winsock catalog holds entries for all installed service providers (like the Name Space Provider for DNS). If an entry is missing or points to a nonexistent DLL, WSA can't instantiate the provider. Resetting the catalog wipes and rebuilds it from defaults.

Advanced fix — 15+ minutes

Repair or rebuild the Name Space Provider registry

If both above steps failed, the problem is in the registry — specifically under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinSock2\Parameters\NameSpace_Catalog5. This is where WSA stores the service name providers. If the DefaultNameSpace value is empty or points to a provider that doesn't exist, you get 0X0000277C.

Open Regedit as Administrator.

Navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinSock2\Parameters\NameSpace_Catalog5

Look at the subkeys — they're named Catalog_Entry00, Catalog_Entry01, etc. Each has a ProviderPath value. Check that each path points to a real DLL. Common ones include %SystemRoot%\system32\nrpsps.dll and %SystemRoot%\system32\dnsrslvr.dll.
If any DLL is missing, you need to restore it. The easiest way is to copy from a healthy machine of the same OS version and build.
Also check the DefaultNameSpace REG_DWORD at the same key level. It should point to the index of the DNS provider (usually 0 or 1). If it's 0xFFFFFFFF or missing, set it to 0.
Reboot.

Why this works: WSA iterates the NameSpace_Catalog5 entries during WSAStartup(). It finds the default namespace provider using DefaultNameSpace, then tries to load its DLL. If the DLL is missing or the index is wrong, WSA returns WSASERVICE_NOT_FOUND because it believes no service provider is available — even if one is. Rebuilding the catalog from a known-good source fixes the registry state.

If nothing works — SFC and DISM

This is your last resort. System File Checker can replace corrupted Winsock DLLs.

Run as Administrator:
```
sfc /scannow
```

Then:

dism /online /cleanup-image /restorehealth

Reboot and test.

Important: If you're on a domain controller, the DNS Client service is critical and should never be stopped. Some admins disable it thinking it's a cache service — it's not. It's the resolver for all name queries on the system.

Real-world scenario: A colleague ran a network benchmark script that turned off dnscache to reduce jitter, then forgot to re-enable it. The next day, every internal tool that used WSA for service discovery failed with 0X0000277C. Quick fix above solved it. Don't disable dnscache on a server.