Fix RPC_S_NO_ENTRY_NAME (0X000006C7) — Binding Missing Entry Name

You hit RPC_S_NO_ENTRY_NAME (0x000006C7)

This one stings because it usually surfaces right when you think your RPC setup is solid — a client call to a server app fails with "The binding does not contain an entry name". The system tells you exactly what's wrong: the binding handle you passed to an RPC function (like RpcBindingToStringBinding or RpcNsBindingLookupBegin) has a null or empty entry name.

The real fix: Build an explicit binding

Stop relying on name service lookups that silently fail. Instead, construct the binding manually with a known endpoint. Here's the code pattern in C using Microsoft RPC:

RPC_STATUS status;
RPC_BINDING_HANDLE hBinding = NULL;
unsigned char *pszStringBinding = NULL;

// Create a string binding — replace with your server's values
status = RpcStringBindingCompose(
    (unsigned char *) "MyInterfaceUUID",  // Interface UUID
    (unsigned char *) "ncacn_ip_tcp",      // Protocol sequence
    (unsigned char *) "192.168.1.100",     // Server address
    (unsigned char *) "5000",              // Endpoint (port)
    NULL,
    &pszStringBinding);

if (status != RPC_S_OK) {
    // Handle error — but this rarely fails
}

// Bind using the string binding
status = RpcBindingFromStringBinding(pszStringBinding, &hBinding);

if (status != RPC_S_OK) {
    // 0x000006C7 can't happen here because we built the string
}

RpcStringFree(&pszStringBinding);

The key line is the RpcStringBindingCompose call. You are explicitly providing every piece: interface UUID, protocol sequence (like ncacn_ip_tcp for TCP/IP), server address, and endpoint. No entry name lookup is needed because the endpoint is baked right in. This bypasses the name service entirely.

Why this works

What's actually happening here is that your original code was doing something like:

status = RpcBindingFromStringBinding(
    (unsigned char *) "MyRpcEntryName", &hBinding);

This string looks like a valid binding string but it's actually just an entry name in the RPC name service database (running on a locator or a domain controller). The RPC runtime takes that string, tries to resolve it via the endpoint mapper or name service, and if the entry doesn't exist or the name service is unreachable, it returns 0x000006C7 because the binding handle it constructs internally has no entry name. The runtime literally can't assign an endpoint without the lookup.

By building the binding with a direct endpoint, you skip the name service. The runtime gets a complete binding path: protocol, address, port, and UUID. No entry name is needed. The error disappears because the binding handle is fully resolved before any RPC call is made.

Less common variations

1. You're using RpcNsBindingImportBegin incorrectly

If you must use the name service, the RpcNsBindingImportBegin function takes an entry name parameter. If you pass NULL or an empty string, you get this error. The fix: provide a valid entry name, or use the explicit binding pattern above.

// Wrong
status = RpcNsBindingImportBegin(RPC_C_NS_SYNTAX_DEFAULT, NULL, ...);

// Right — use a specific entry name like "/.:/MyService"
status = RpcNsBindingImportBegin(RPC_C_NS_SYNTAX_DEFAULT,
    (unsigned char *) "/.:/MyService", ...);

2. The server didn't register its endpoint with the RPC locator

Even if you use the name service, the server must call RpcNsBindingExport to register its binding. If the export failed silently (e.g., the locator service isn't running), the client gets 0x000006C7. Check the locator service status: sc query RpcLocator. On modern Windows Server (2016+), locator is off by default. Don't rely on it.

3. Interface UUID mismatch

A subtler variant: the server registers with UUID 12345678-1234-1234-1234-123456789abc, but the client's binding string uses a different UUID. The RPC runtime fails at lookup time because the name service has no matching entry. The fix: verify the UUID on both sides.

Prevention

Three rules to stop seeing 0x000006C7:

1. Avoid the name service entirely unless you really need dynamic discovery. Explicit endpoints are simpler and more reliable. Hardcode the port or use a config file.
2. If you must use name service, verify the locator is running and the server exported the binding. Test with rpcexts.dll or Wireshark to confirm the endpoint mapper response.
3. Always check RPC status codes after every binding call. Don't assume success. Log the failure code — it will save you hours later when the error shifts subtly.

You don't need to "understand the name service deeply" to fix this. You just need to stop using it. Explicit binding is the direct path.