---
name: "Ns_ConnReturnOpenChannel"
section: "3aolserver"
platform: "linux"
package: "aolserver4-dev"
version: "4.5.1-18.1"
release: "Debian 9 (Stretch)"
platforms: ["linux"]
url: "https://new.carta.tech/Ns_ConnReturnOpenChannel/3aolserver"
---

# Ns\_ConnReturnOpenChannel(3aolserver)

Routines to send open file content

```

```

## NAME

Ns\_ConnReturnOpenChannel, Ns\_ConnReturnOpenFd, Ns\_ConnReturnFdEx, Ns\_ConnReturnOpenFile - Routines to send open file content

## SYNOPSIS

```
#include "ns.h"
int

int
Ns_ConnReturnOpenChannel(conn, status, type, chan, len)

int
Ns_ConnReturnOpenFd(conn, status, type, fd, len)

int
Ns_ConnReturnOpenFdex(conn, status, type, fd, off, len)

int
Ns_ConnReturnOpenFile(conn, status, type, fp, len)
```

## ARGUMENTS

- Tcl\_Channel *chan* (in)

  Pointer to Tcl\_Channel open for read.

- Ns\_Conn *conn* (in)

  Pointer to open connection.

- FILE *\*fp* (in)

  Pointer to stdio FILE open for read.

- off\_t *off* (in)

  Seek offset.

- int *fd* (int)

  File descriptor open for read.

- int *status* (in)

  HTTP status code.

- char *\*type* (in)

  Pointer to mimetype string.

  ```

  ```

## DESCRIPTION

These routines are used to generate complete responses, including headers, status codes, content types, and the content copied from the given open file. They all return a status code which is NS\_OK if the response was sent or NS\_ERROR if an underlying call to sent the content failed.  The response will include the given HTTP *status* code, a *content-type* header with the given *type*, and a *content-length* header with the length specified by *len*.  No character output encoding or gzip compression is performed on the content.

For **Ns\_ConnReturnOpenFdEx**, copying begins at the offset specified by the *off* argument Otherwise, these routines copy from the current read offset in the underlying open file.  No attempt is made to serialize access to the underlying object so independent open file objects and/or mutex locking is necessary if the same file is being sent simultaneously to multiple clients.

## NOTES

- Windows Support

  The **Ns\_ConnReturnOpenFdEx** routine is not currently supported on Windows.  When called on Windows, it will always return NS\_ERROR.

- Truncated Result

  The server will construct a *content-length* header based on the given *len* argument. However, the server will send the content with an underlying call to a cooresponding **Ns\_ConnSend** function, e.g., **Ns\_ConnSendFd** for **Ns\_ConnReturnOpenFd**. These functions will send the requested content or all remaining content in the open file if less bytes are avilable without reporting an error due to the truncated response.  As the headers will have already been flushed before sending the content in this case, the *content-length* header will not be consistent with the actual bytes sent.  If it is not possible to ensure the remaining bytes will be equal or greater to the requested bytes to send, it is possible to specify -1 for *len* to supress the *content-length* header entirely.  Most browsers will accept this resonse and simply calculate the length from the bytes receieved up until the socket is closed.

- Performance Consideration

  As mentioned, these routines use underlying **Ns\_ConnSendFd** style routines to copy and send the content from open files.  This is not the approach used by the builtin file-serving code (aka the "fastpath").  The fastpath operates with filenames, not open file objects, and maintains a cached of pre-read or memory mapped regions to accelerate the common case of rapidly sending reasonably sized content to multiple, simultaneous clients.  The **Ns\_ConnReturnFile** routine utilizes the underlying fastpath and thus could be a faster means to send static files than directly opening files and calling these API's.

## SEE ALSO

[Ns\_ConnReturnFile(3)](/Ns_ConnReturnFile/3.md), Ns\_ConnFlush(3), [Ns\_ConnSendFd(3)](/Ns_ConnSendFd/3.md), [Ns\_ConnReturnData(3)](/Ns_ConnReturnData/3.md)

## KEYWORDS

connnection, response, file