tftp

Streaming TFTP client and Server

WARNING

The implementation it's already done, you can GET and PUT files correctly. However, some optimizations must still be done, so for your safety don't use it in production or development, just for testing purposes. It will be ready when it reaches the version 0.1.0.

Full-featured streaming TFTP client and server. It supports most of the RFCs:

• 1350 - The TFTP protocol ✓
• 2347 - Option extension ✓
• 2348 - Blocksize option ✓
• 2349 - Timeout Interval and Transfer Size Options ✓
• 2090 - Multicast option ✗
• 3617 - Uniform Resource Identifier (URI) ✓
• De facto (draft) - Windowsize option ✓
• De facto - Rollover option ✓
• mail and netascii transfer modes ✗

CLIENT | SERVER

Per se, the TFTP is a lock-step protocol built on top of UDP for transferring files between two machines. It was useful in the past but nowadays it's practically an obsolete legacy protocol useful in a very few scenarios. Without the extensions support, the RFC says that a file bigger than 32MB cannot be sent. This limit can be incremented to 91.74MB if both machines agree to use a block size of 1468 bytes, the MTU size before IP fragmentation in Ethernet networks. Also, the transfer speed is pretty slow due to the lock-step mechanism, one acknowledgement for each packet.

However, there are two de facto extensions that can boost the transfer speed and remove the size limit: the rollover and the window.

This module it's perfectly integrated with Node.js, providing an streaming interface for GETting and PUTing files very easily. No configuration is needed. By default the client tries to negotiate with the server the best possible configuration. If that's not possible it simply fallbacks to the original lock-step TFTP implementation. The server also supports both the enhanced features and the classic lock-step implementations.

It can be installed locally and used programmatically, but it can be also installed globally and used directly from the console as a CLI utility (client only).

Special thanks

Patrick Masotta (author of the Serva application and the internet draft about the windowsize option).

Warning! UDP packet loss in Windows

Currently, in Windows there is a problem concerning the buffering of the received network packets (#6696). Basically, when the buffer is full, all the subsequent incoming packets are dropped, so they are never consumed by Node.js. This scenario can be reproduced by configuring a window bigger than 6 blocks with the default block size. So the advice is: do NOT increment the default window size (4) in the Windows platform until this bug is solved.

CLIENT

module.createClient([options]) : Client

Documentation

• Streams
• Global installation

Objects

• Client
• GetStream and PutStream

Streams

For the sake of simplicity the following examples omit the error handling. See the streams.js example or the source code of the get() and put() functions for more information.

GET remote → local

var get = client.createGetStream ("remote-file");
var write = fs.createWriteStream ("local-file");

get.pipe (write);

PUT local → remote

var read = fs.createReadStream ("local-file");
var put = client.createPutStream ("remote-file", { size: totalSize });

read.pipe (put);

Global installation

npm install tftp -g

Then you can access to the ntftp binary.

There are basically two ways to use it: with or without a shell.

Without a shell

Best for individual transfers.

$ ntftp get [options] <rfc3617_uri> [<local>]
$ ntftp put [options] [<local>] <rfc3617_uri>

For example:

$ ntftp get tftp://localhost/remote-file
remote-file             42.2 MiB   32.6M/s 00:12 [###·····················]  13%

$ ntftp put my/local-file tftp://localhost/remote-file
my/local-file          148.8 MiB   30.9M/s 00:07 [###########·············]  45%

For more information type ntftp get|put -h.

With a shell

Best for multiple transfers, basically because the same server address and options are reused.

$ ntftp [options] <host>[:<port>]

For example:

$ ntftp localhost
> get remote-file
remote-file             42.2 MiB   32.6M/s 00:12 [###·····················]  13%
> put my/local-file remote-file
my/local-file          148.8 MiB   30.9M/s 00:07 [###########·············]  45%

For more information type ntftp -h and get|put -h.

module.createClient([options]) : Client

Returns a new Client instance.

var client = tftp.createClient ({
  host: "10.10.10.10",
  port: 1234
});

Options:

• host - String
  The address. Default is localhost.

• port - Number
  The port. Default is 69.

• blockSize - Number
  The size of the DATA blocks. Valid range: [8, 65464]. Default is 1468, the MTU size before IP fragmentation in Ethernet networks.

• windowSize - Number
  The size of each window. The window size means the number of blocks that can be sent/received without waiting an acknowledgement. Valid range: [1, 65535]. Default is 4.

  Comparison of transfer times:

  Window size	Improvement
  1	-0%
  2	-49%
  3	-64%
  4	-70%
  5	-73%
  6	-76%

  Take into account that with a bigger window more elements must be sorted (remember that UDP doesn't sort the incoming packets). This doesn't slow down the transfer very much but it requires more CPU. A window size of 4 is a good trade between transfer speed and CPU usage.

  Right now a window size of 6 is the maximum in Windows due to the packet loss issue. With a window size of 7 or greater a lot of timeouts and retransmissions begin to occur, so the recommendation is to use a window size of 4, the default value.

• retries - Number
  How many retries must be done before emitting an error. Default is 3.

• timeout - Number
  Milliseconds to wait before a retry. Default is 3000.

Client

Each of the following methods take an options parameter. One option available is userExtensions, an object with properties that can be sent with a GET or PUT operation. For example:

var options = {
  userExtensions: {
    foo: "bar",
    num: 2
  }
}

The server may ignore or not these extensions, this feature is server-dependent. Please note that the TFTP algorithm cannot be modified. For example, you can implement a basic authentication; the client could send the extensions user and password and the server could validate the user and accept or deny the request. The extensions are transmitted in plain text.

The extensions timeout, tsize, blksize, windowsize and rollover are reserved and cannot be used.

Methods

• Client#createGetStream(remoteFile[, options]) : GetStream
• Client#createPutStream(remoteFile, options) : PutStream
• Client#get(remoteFile[, localFile][, options], callback) : undefined
• Client#put(localFile[, remoteFile][, options], callback) : undefined

Client#createGetStream(remoteFile[, options]) : GetStream

Returns a new GetStream instance.

Options:

• highWaterMark - Number
  Buffer size. Default is 16KB.
• md5sum - String
  MD5 sum for validating the integrity of the file.
• sha1sum - String
  SHA1 sum for validating the integrity of the file.
• userExtensions - Object
  Custom extensions to send with the request. More information.

var get = client.createGetStream ("file");

Client#createPutStream(remoteFile, options) : PutStream

Returns a new PutStream instance.

Options:

• highWaterMark - Number
  Buffer size. Default is 16KB.
• size - String
  Total size of the file to upload. This option is required.
• userExtensions - Object
  Custom extensions to send with the request. More information.

var put = client.createPutStream ("file", { size: 1234 });

Client#get(remoteFile[, localFile][, options], callback) : undefined

Downloads a file from the server. If the local filename is missing the filename of the remote file is used.

Options:

• highWaterMark - Number
  Buffer size. Default is 16KB.
• md5sum - String
  MD5 sum for validating the integrity of the file.
• sha1sum - String
  SHA1 sum for validating the integrity of the file.
• userExtensions - Object
  Custom extensions to send with the request. More information.

//tftp://<host>/file -> file
client.get ("file", function (error){
  if (error) return console.error (error);
  ...
});

Client#put(localFile[, remoteFile][, options], callback) : undefined

Uploads a file to the server. If the remote filename is missing the filename of the local file is used.

Options:

• highWaterMark - Number
  Buffer size. Default is 16KB.
• userExtensions - Object
  Custom extensions to send with the request. More information.

//file -> tftp://<host>/file
client.put ("file", function (error){
  if (error) return console.error (error);
  ...
});

GetStream and PutStream

The GetStream inherits from a Readable stream and the PutStream from a Writable stream.

Events

• abort
• close
• end
• error
• finish
• stats

Methods

• abort() : undefined

abort

Arguments: none.

Emitted when abort() is called and the transfer has been aborted.

close

Arguments: none.

Emitted when the underlying socket has been closed. It is emitted always and before any other event (error, abort, end or finish).

end

Arguments: none.

Emitted by the GetStream when the file download finishes.

error

Arguments: error.

Emitted when an error occurs. The stream is closed automatically.

finish

Arguments: none.

Emitted by the PutStream when the file upload finishes.

stats

Arguments: stats.

Emitted when the client negotiates the best possible configuration. When it is emitted the transfer still hasn't begun.

stats is an object similar to this:

{
  blockSize: 1468,
  windowSize: 4,
  size: 105757295,
  userExtensions: null,
  file: 'file',
  retries: 3,
  timeout: 3000,
  localAddress: "0.0.0.0",
  localPort: 55146,
  remoteAddress: "127.0.0.1",
  remotePort: 55147
}

When the GetStream emits a stats event, the size property is not guaranteed to be a Number because the server may not implement all the RFCs. The size of the file is obtained during the negotiation but not all the servers are able to negotiate. In these cases the size is null.

The userExtensions property holds an object with the custom extensions sent by the server in response to the custom extensions sent with the request. Most of the TFTP servers don't let you respond with custom extensions when in fact this is a feature explained in the RFCs, so unless the TFTP server allows you to respond with custom extensions, this property will be always null. Of course, the server included with this module let you set the user extensions to send back to the client.

abort() : undefined

Aborts the current transfer.

SERVER

module.createServer([options][, requestListener]) : Server

Documentation

• Global installation

Objects

• Server
• GetStream and PutStream

Global installation

npm install tftp -g

Then you can access to the ntftp binary.

Use the -l|--listen[=ROOT] option to start the server. By default the root directory is ..

$ ntftp [options] <host>[:<port>] -l|--listen=ROOT

For example:

$ ntftp localhost -l

This command starts a server listening on localhost:69 and root ..

module.createServer([options][, requestListener]) : Server

Returns a new Server instance.

var server = tftp.createServer ({
  host: "10.10.10.10",
  port: 1234,
  root: "path/to/root/dir",
  denyPUT: true
});

The requestListener is a function which is automatically added to the request event.

Options:

It has the same options as the createClient() function with the addition of:

• root - String
  The root directory. Default is ..
• denyGET - Boolean
  Denies all the GET operations. Default is false.
• denyPUT - Boolean
  Denies all the PUT operations. Default is false.

Setting the options denyGET or denyPUT are more efficient than aborting the request from inside the request listener.

Server

Events

• close
• connection
• error
• listening
• request

Methods

• close() : undefined
• listen() : undefined
• requestListener(req, res) : undefined

Properties

• root

close

Arguments: none.

Emitted when the server closes. No new requests are accepted. Note that the current transfers are not aborted. If you need to close the server gracefully, look at this example.

error

Arguments: error.

Emitted when an error occurs receiving data. The server is not closed.

listening

Arguments: none.

Emitted when the server has been bound after calling listen().

request

Arguments: req, res.

Emitted when a new request has been received. All the connection objects that are emitted can be aborted at any time.

req is an instance of a GetStream and res is an instance of a PutStream.

This event is emitted after some minor validations. If the path is directory or the user tries to access a file outside the root directory (eg.: ../file), the request fails. Furthermore, in the case of GET operations, the request automatically sends an error to the client if the file doesn't exist, so if you use a custom request listener, you don't need to check whether the file exists because this validation was already done.

close() : undefined

Closes the server and stops accepting new connections.

listen() : undefined

Starts accepting new connections.

requestListener(req, res) : undefined

This function must NOT be called from outside a request listener. This function is the default request listener, it automatically handles the GET and PUT requests.

root

The root path.

GetStream and PutStream

When the request event is emitted, a new GetStream and PutStream instances are created. These streams are similar to the streams used in the client but with one difference, the GetStream (req) acts like a "connection" object. All the events from the PutStream (res) are forwarded to the req object, so you don't need to attach any event to the res object.

The GetStream has two additional properties:

• method - String
  The transfer's method: GET or PUT.
• file - String
  The path of the file. The directories are not created recursively if they don't exist.

The PutStream has one additional method:

• setUserExtensions(userExtensions) : undefined

  Sets the user extensions to send back to the client in response to the received ones. You cannot send extensions different from the ones that are sent by the client.

  As said previously, the TFTP protocol doesn't have any built-in authentication but thanks to the user extensions you can implement a simple authentication mechanism as showed here.

  Look at the examples for more details.