Application Development Documentation / Guides

Step-By-Step - Common Client Libraries

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This document step-by-step how to get a minimal [NFD](https://github.com/named-data/NFD) running so you can start writing applications to use the NDN [Common Client Libraries](http://named-data.net/doc/ndn-ccl-api/) ([NDN-CPP](https://github.com/named-data/ndn-cpp), [NDN-JS](https://github.com/named-data/ndn-js), [PyNDN](https://github.com/named-data/PyNDN2), [jNDN](https://github.com/named-data/jndn)).

# Prerequisites

## OS X 10.7.3, OS X 10.8.4, OS X 10.9

* Install Xcode.

* (OS X 10.7.3, OS X 10.8.4 only) In Xcode Preferences > Downloads, install "Command Line Tools".

* Install MacPorts from http://www.macports.org/install.php

In a terminal, enter:

    sudo port install pkgconfig boost sqlite3 libcryptopp libpcap

To build NFD, we need `/usr/local/lib/pkgconfig` in the environment variable `PKG_CONFIG_PATH`, so we set it here. If you close your terminal before building NFD, you should set this again.

    export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig

## Ubuntu 12.04

In a terminal, enter:

    sudo apt-get install build-essential

    sudo apt-get install git libssl-dev libsqlite3-dev libcrypto++-dev libpcap-dev libboost1.48-all-dev

## Ubuntu 13.10, Ubuntu 14.04 and Raspbian Wheezy (Rapberry Pi)

In a terminal, enter:

    sudo apt-get install build-essential

    sudo apt-get install git libssl-dev libsqlite3-dev libcrypto++-dev libpcap-dev libboost-all-dev

### Raspberry Pi

To run NFD on the Raspberry Pi, you need to enable IPv6 support. Enter `sudo nano /etc/modules` (or use your favorite editor). Add the following line to `/etc/modules`:

    ipv6

Reboot your Raspberry Pi.

(If you don't want to enable IPv6 support on the Raspberry Pi, you can disable IPv6 in NFD. After installing NFD, replace `enable_v6 yes` with `enable_v6 no` in the `tcp` and `udp` sections of `/usr/local/etc/ndn/nfd.conf` .)

# Build/Install NFD

These are steps to [build/install NFD](http://named-data.net/doc/NFD/current/INSTALL.html) which works with NFD.  In a terminal, enter:

    git clone https://github.com/named-data/ndn-cxx.git

    git clone https://github.com/named-data/NFD.git

    cd ndn-cxx

    ./waf configure

If waf says "program doxygen not found", "program sphinx-build not found" or "library rt not found", it is OK.

    ./waf

    sudo ./waf install

    cd ..

    cd NFD

    git submodule init && git submodule update

    ./waf configure

If waf says "libndn-cxx not found", then set `PKG_CONFIG_PATH` as shown in the Prerequisites above.

    ./waf

    sudo ./waf install

    cd ..

The NFD programs are installed in `/usr/local/bin` . The NFD configuration file is in `/usr/local/etc/ndn` .  Copy the sample configuration file to make it the default:

    sudo cp /usr/local/etc/ndn/nfd.conf.sample /usr/local/etc/ndn/nfd.conf

# Configure NFD

NFD provides mechanisms to enable strict authorization for all management commands.  In particular, one can authorize only a specific public key to create new Faces or to change the strategy choice for specific namespaces.

For more information about how to generate a private/public key pair, generate a self-signed certificate, and use this self-signed certificate to authorize NFD management commands, refer to [NFD Configuration Tips](http://named-data.net/doc/NFD/current/README.html).

In the sample configuration file, all authorization is disabled, effectively allowing anybody on the local machine to issue NFD management commands. **The sample file is intended only for demo purposes and MUST NOT be used in a production environment.**

## Start NFD

If you have NDNx or ndnd-tlv on your computer, you don't need to uninstall. But if they are running, you need to stop them:

    ndnd-tlv-stop

    ndndstop

Open a new terminal window (so you can watch the NFD messages) and enter:

    nfd-start

On OS X it may ask for your keychain password or ask "nfd wants to sign using key in your keychain." Enter your keychain password and click Always Allow.

Later, you can stop NFD with `nfd-stop` .

## Add a route to another NFD host (optional)

The previous instructions are good for testing on the local host. If you want to route an interest to another NFD host, in a terminal enter:

    nfdc register /ndn udp://<other host>

where `<other host>` is the name or IP address of the other host (e.g., `spurs.cs.ucla.edu`). The "/ndn" means that NFD will forward all interests that start with `/ndn` through the face to the other host.  If you only want to forward interests with a certain prefix then use it instead of "/ndn".

This only forwards interests to the other host, but there is no "back route" for the other host to forward interests to you. For that, you must go to the other host and use `nfdc` to add the route. (The "back route" can also be automatically configured with `nfd-autoreg`.  For more information refer to [nfd-autoreg manpage](http://named-data.net/doc/NFD/current/manpages/nfd-autoreg.html).)

# Install the Common Client Library

If you haven't done so, get the library from GitHub and follow the INSTALL instructions for your language:

* C++: [ndn-cpp](https://github.com/named-data/ndn-cpp) ([INSTALL](https://github.com/named-data/ndn-cpp/blob/master/INSTALL) instructions)

* Python: [PyNDN2](https://github.com/named-data/PyNDN2) ([INSTALL](https://github.com/named-data/PyNDN2/blob/master/INSTALL) instructions)

* JavaScript: [ndn-js](https://github.com/named-data/ndn-js) ([INSTALL](https://github.com/named-data/ndn-js/blob/master/INSTALL) instructions)

# Send an Interest to receive a Data packet

The example program "test get async" is a simple program to send some interests and get a data packet.  Here they are on the various languages:

* C++: [`test-get-async.cpp`](https://github.com/named-data/ndn-cpp/blob/master/tests/test-get-async.cpp)

* Python: [`test_get_async.py`](https://github.com/named-data/PyNDN2/blob/master/tests/test_get_async.py)

* JavaScript (browser): [`test-get-async.html`](https://github.com/named-data/ndn-js/blob/master/tests/browser/test-get-async.html)

* JavaScript (node): [`fetch.js`](https://github.com/named-data/ndn-js/blob/master/tests/node/fetch.js)

The main calls to the API are (using Python for example):

Call the [Face constructor](http://named-data.net/doc/ndn-ccl-api/face.html#face-constructors) and specify the host.

    face = Face("aleph.ndn.ucla.edu")

Create a [Name](http://named-data.net/doc/ndn-ccl-api/name.html#name-constructor-from-uri) for the Interest, using a Name URI.

    name1 = Name("/ndn/edu/ucla/remap/ndn-js-test/howdy.txt")

Call [expressInterest](http://named-data.net/doc/ndn-ccl-api/face.html#face-expressinterest-method-from-name), passing in the callbacks for onData and onTimeout.

    face.expressInterest(name1, counter.onData, counter.onTimeout)

Start an event loop to keep calling [processEvents](http://named-data.net/doc/ndn-ccl-api/face.html#face-processevents-method) until the application is finished.

Your application should make sure that it calls processEvents in the same thread as expressInterest (which also modifies the pending interest table).

    while counter._callbackCount < 3:

        face.processEvents()

        # We need to sleep for a few milliseconds so we don't use 100% of the CPU.

        time.sleep(0.01)