embassy/examples/std

Running the embassy-net examples

To run net, tcp_accept, net_udp and net_dns examples you will need a tap interface. Before running these examples, create the tap99 interface. (The number was chosen to hopefully not collide with anything.) You only need to do this once every time you reboot your computer.

cd $EMBASSY_ROOT/examples/std/
sudo sh tap.sh

The example net_ppp requires different steps that are detailed in its section.

net example

For this example, you need to have something listening in the correct port. For example nc -lp 8000.

Then run the example located in the examples folder:

cd $EMBASSY_ROOT/examples/std/
cargo run --bin net -- --tap tap99 --static-ip

tcp_accept example

This example listen for a tcp connection.

First run the example located in the examples folder:

cd $EMBASSY_ROOT/examples/std/
cargo run --bin tcp_accept -- --tap tap99 --static-ip

Then open a connection to the port. For example nc 192.168.69.2 9999.

net_udp example

This example listen for a udp connection.

First run the example located in the examples folder:

cd $EMBASSY_ROOT/examples/std/
cargo run --bin net_udp -- --tap tap99 --static-ip

Then open a connection to the port. For example nc -u 192.168.69.2 9400.

net_dns example

This example queries a DNS for the IP address of www.example.com.

In order to achieve this, the tap99 interface requires configuring tap99 as a gateway device temporarily.

For example, in Ubuntu you can do this by:

1. Identifying your default route device. In the next example eth0

ip r | grep "default"
default via 192.168.2.1 dev eth0 proto kernel metric 35

2. Enabling temporarily IP Forwarding:

sudo sysctl -w net.ipv4.ip_forward=1

3. Configuring NAT to mascarade traffic from tap99 to eth0

sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sudo iptables -A FORWARD -i tap99 -j ACCEPT
sudo iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

4. Then you can run the example located in the examples folder:

cd $EMBASSY_ROOT/examples/std/
cargo run --bin net_dns -- --tap tap99 --static-ip

net_ppp example

This example establish a Point-to-Point Protocol (PPP) connection that can be used, for example, for connecting to internet through a 4G modem via a serial channel.

The example creates a PPP bridge over a virtual serial channel between pty1 and pty2 for the example code and a PPP server running on the same computer.

To run this example you will need:

• ppp (pppd server)
• socat (socket CAT)

To run the examples you may follow the next steps:

1. Save the PPP server configuration:

sudo sh -c 'echo "myuser $(hostname) mypass 192.168.7.10" >> /etc/ppp/pap-secrets'

2. Create a files pty1 and pty2 and link them

cd $EMBASSY_ROOT/examples/std/
socat -v -x PTY,link=pty1,rawer PTY,link=pty2,rawer

3. open a second terminal and start the PPP server:

cd $EMBASSY_ROOT/examples/std/
sudo pppd $PWD/pty1 115200 192.168.7.1: ms-dns 8.8.4.4 ms-dns 8.8.8.8 nodetach debug local persist silent

4. Open a third terminal and run the example

cd $EMBASSY_ROOT/examples/std/
RUST_LOG=trace cargo run --bin net_ppp -- --device pty2

5. Observe the output in the second and third terminal
6. Open one last terminal to interact with net_ppp example through the PPP connection

# ping the net_ppp client
ping 192.168.7.10
# open an tcp connection
nc 192.168.7.10 1234
# Type anything and observe the output in the different terminals