# PR_GetProtoByNumber

Looks up a protocol entry based on protocol's number.

## Syntax

```{code}
#include <prnetdb.h>

PRStatus PR_GetProtoByNumber(
  PRInt32 protocolnumber,
  char* buffer,
  PRInt32 bufsize,
  PRProtoEnt* result);
```

### Parameters

The function has the following parameters:

`protocolnumber`

: The number assigned to the protocol.

`buffer`

: A pointer to a scratch buffer for the runtime to return result. This
  buffer is allocated by the caller.

`bufsize`

: Number of bytes in the `buffer` parameter. The buffer must be at
  least {ref}`PR_NETDB_BUF_SIZE` bytes.

`result`

: On input, a pointer to a {ref}`PRNetAddr` structure. On output, this
  structure is filled in by the runtime if the function returns
  `PR_SUCCESS`.

### Returns

The function returns one of the following values:

- If successful, `PR_SUCCESS`.
- If unsuccessful, `PR_FAILURE`. You can retrieve the reason for the
  failure by calling {ref}`PR_GetError`.