Host
====

The Host component is analogous to a host, or node in a classical network. Hosts in QuNetSim act either as a routing
node that can relay packets through the network, or they can act as a node that runs a specific protocol. It is up
to the protocol developer to configure how the nodes behave. In most cases, once the network is established,
users will run specific protocols on the nodes. In the examples we see how to accomplish this.

One other feature of a host is that they can also sniff packets, or eavesdrop on channels to manipulate the payload
of the packet. For example, they can apply random noise to any qubit or change the classical messages that are routed
through them. We see an example of that in the examples section.


The most commonly used methods for Hosts are:

* :code:`add_connection(host_id)`
    * Add a classical and quantum connection to the host with id *host_id*
* :code:`get_classical(host_id, wait=N)`
    * Get a classical message from sender with host_id *host_id* and wait *N* seconds for it
* :code:`get_qubit(host_id, wait=N)`:
    * Get a data qubit from sender with host_id *host_id* and wait *N* seconds for it
* :code:`get_qubits(host_id)`:
    * Get all data qubits from sender with host_id *host_id*
* :code:`get_epr(host_id, q_id=q_id)`:
    * Get EPR pair with qubit ID *q_id* from sender with host_id *host_id*. If *q_id=None* then get the first free EPR pair
* :code:`get_epr_pairs(host_id)`:
    * Get all EPR pairs established with host with host_id *host_id*
* :code:`send_classical(host_id, message, await_ack=<bool>)`:
    * Send the classical message *message* to host with host_id *host_id*. Block until ACK arrives if *await_ack=True*
* :code:`send_key(host_id, key_size)`:
    * Send a secret key via QKD of length *key_size* to host with ID *receiver_id*.
* :code:`send_qubit(host_id, qubit, await_ack=<bool>)`:
    * Send qubit *qubit* to host with host_id *host_id*. Block until ACK arrives if *await_ack=True*.
* :code:`send_superdense(host_id, message, await_ack=<bool>)`:
    * Send a message (one of '00', '01', '10', or '11') as a superdense message
* :code:`send_teleport(host_id, qubit, await_ack=<bool>)`:
    * Teleport qubit *qubit* to host with host_id *host_id*.
* :code:`send_epr(host_id, qubit_id=<None>, await_ack=<bool>)`:
    * Creates a shared EPR pair with the host with host_id *host_id*.
* :code:`send_ghz([host_id_list], qubit_id=<None>, await_ack=<bool>)`:
    * Creates a shared GHZ state with all hosts in the list [host_id_list].
* :code:`shares_epr(host_id)`:
    * Returns if the host shares entanglement already with host with host_id *host_id*
* :code:`run_protocol(protocol, protocol_params)`:
    * Run the function *protocol* with the parameters *protocol_params*.


.. automodule:: qunetsim.components.host
   :members: