OVMS3-idf/examples/protocols/sockets/tcp_client/README.md

# TCP Client example

(See the README.md file in the upper level 'examples' directory for more information about examples.)

The application creates a TCP socket and tries to connect to the server with predefined IP address and port number. When a connection is successfully established, the application sends message and waits for the answer. After the server's reply, application prints received reply as ASCII text, waits for 2 seconds and sends another message.

## How to use example

In order to create TCP server that communicates with TCP Client example, choose one of the following options.

There are many host-side tools which can be used to interact with the UDP/TCP server/client. 
One command line tool is [netcat](http://netcat.sourceforge.net) which can send and receive many kinds of packets. 
Note: please replace `192.168.0.167 3333` with desired IPV4/IPV6 address (displayed in monitor console) and port number in the following command.

In addition to those tools, simple Python scripts can be found under sockets/scripts directory. Every script is designed to interact with one of the examples.

### TCP server using netcat
```
nc -l 192.168.0.167 3333
```

### Python scripts
Script example_test.py could be used as a counter part to the tcp-client project, ip protocol name (IPv4 or IPv6) shall be stated as argument. Example:

```
python example_test.py IPv4
```
Note that this script is used in automated tests, as well, so the IDF test framework packages need to be imported;
please add `$IDF_PATH/tools/ci/python_packages` to `PYTHONPATH`.

## Hardware Required

This example can be run on any commonly available ESP32 development board.

## Configure the project

```
idf.py menuconfig
```

Set following parameters under Example Configuration Options:

* Set `IP version` of example to be IPV4 or IPV6.

* Set `IPV4 Address` in case your chose IP version IPV4 above.

* Set `IPV6 Address` in case your chose IP version IPV6 above.

* Set `Port` number that represents remote port the example will connect to.

Configure Wi-Fi or Ethernet under "Example Connection Configuration" menu. See "Establishing Wi-Fi or Ethernet Connection" section in [examples/protocols/README.md](../../README.md) for more details.

## Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

```
idf.py -p PORT flash monitor
```

(To exit the serial monitor, type ``Ctrl-]``.)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.


## Troubleshooting

Start server first, to receive data sent from the client (application).