API overview — pyptlib 0.0.1 documentation

# pyptlib documentation

## API overview

Be sure to read `API.rst` and `glossary.rst` before reading this file.

## General Overview

Applications begin by initializing pyptlib.

Then pyptlib informs the application about which transports it should spawn, in which ports they should listen for connections, etc.

Then the application launches the appropriate transports as instructed, and for each transport it reports to pyptlib whether it was launched successfully or not. Finally, the application announces to pyptlib that it finished launching transports.

From that point and on the application should forget about pyptlib and start accepting connections.

## Detailed API Overview

### 0) Find if it’s a client or a server

An application using pyptlib should start by calling `pyptlib.util.checkClientMode()` to learn whether Tor wants it to run as a client or as a server.

### 1) Get transport information from Tor

If Tor wants the application to run as a client, the next step is to run `pyptlib.client.init()`. Otherwise, the application should run `pyptlib.server.init()`.

`init()` expects to be passed a list with the names of the transports your application supports.

The application should be prepared for `pyptlib.config.EnvError`, which signifies that the environment was not prepared by Tor.

The application should store the return value of the `init()` function.

Consider an example of the fictional application rot0r which implements the pluggable transports rot13 and rot26. If rot0r, in step 1, learned that Tor expects it to act as a client, it should now do:

    import pyptlib.client
    import pyptlib.config

    try:
        managed_info = pyptlib.client.init(["rot13", "rot26"])
    except pyptlib.config.EnvError, err:
        print "pyptlib could not bootstrap ('%s')." % str(err)

### 2) Launch transports

#### Client case (skip if you are a server)

If your application is a client, the return value of `pyptlib.client.init()` is a dictionary of the format:

Key | Type | Value
--- | --- | ---
state_loc | string | Directory where the managed proxy should dump its state files (if needed).
transports | list | Strings of the names of the transports that should be launched. The list can be empty.

Your application should then use the transports key to learn which transports it should launch.

Proceeding with the previous example:

    if 'rot13' in managed_info['transports']:
        launch_rot13_client()
    if 'rot26' in managed_info['transports']:
        launch_rot26_client()

Note

Since the application runs as a client, it should launch a SOCKS server in the upstream side of the proxy.

#### Server case (skip if you are a client):

If your application is a server, the return value of `pyptlib.server.init()` is a dictionary of the format:

Key | Type | Value
--- | --- | ---
state_loc | string | Directory where the managed proxy should dump its state files (if needed).
orport | tuple | (ip,port) tuple pointing to Tor’s ORPort.
ext_orport | tuple | (ip,port) tuple pointing to Tor’s Extended ORPort. None if Extended ORPort is not supported.
transports | dict | A dictionary ‘transport => (ip,port)’ where ‘transport’ is the name of the transport that should be spawned, and ‘(ip,port)’ is the location where the transport should bind. The dictionary can be empty.

Your application should then use the transports key and attempt to launch the appropriate transports. Furthermore, since the application runs as a server, it should push data to Tor’s ORPort. The TCP/IP location of the ORPort is provided in the orport key.

Proceeding with the previous example:

    if 'rot13' in managed_info['transports']:
        launch_rot13_server(managed_info['transports']['rot13'], managed_info['orport'])
    if 'rot26' in managed_info['transports']:
        launch_rot26_server(managed_info['transports']['rot26'], managed_info['orport'])

### 3) Report results back to Tor.

For every transport that the application launches, it reports to pyptlib whether it was launched successfully or not. This way, Tor is informed on whether a transport is expected to work or not.

#### Client case (skip if you are a server):

Everytime a transport is successfully launched, the application calls `pyptlib.client.reportSuccess()` with the name of the transport that was launched, the address where it is listening for connections, and the SOCKS version that the upstream SOCKS server supports.

For example, if rot13 was launched successfully, waits for connections in ‘127.0.0.1:42042’ and supports SOCKSv4, the appropriate call would be:

    pyptlib.client.reportSuccess('rot13', 5, ('127.0.0.1', 42042))

Everytime a transport failed to launch, the application calls `pyptlib.client.reportFailure()` with the name of the transport and a message.

For example, if rot26 failed to launch, the appropriate call would be:

    pyptlib.client.reportFailure('rot26', 'Could not bind to 127.0.0.1:666 (Operation not permitted)')

#### Server case (skip if you are a client):

Everytime a transport is successfully launched, the application calls `pyptlib.server.reportSuccess()` with the name of the transport that was launched, and the address where it is listening for connections.

For example, if rot13 was launched successfully and waits for connections in ‘127.0.0.1:42042’, the appropriate call would be:

    pyptlib.server.reportSuccess('rot13', ('127.0.0.1', 42042))

Everytime a transport failed to launch, the application calls `pyptlib.server.reportFailure()` with the name of the transport and a message.

For example, if rot26 failed to launch, the appropriate call would be:

    pyptlib.server.reportFailure('rot26', 'Could not bind to 127.0.0.1:666 (Operation not permitted)')

### 4) Stop using pyptlib and start accepting connections

When the application finishes launching connections, it should call `pyptlib.client.reportEnd()` (or `pyptlib.server.reportEnd()`), to announce to pyptlib that all transports were launched. This way, Tor knows that it can start pushing traffic to the application.

After this point, pyptlib has no other use.