esp32 tcp 服务端和客户端程序

### this sample would make your ESP32 interact with any other platform using JSON exchange format ## Part 1 : main features 1. support multiple tcp client connections, user could define connections by MAX_LIENT_NUMBER 2. support TCP stream group packet, user could define it by TCP_STREAM_HEAD_CHECK 3. support JSON parsing sample and respond to client samplle 4. independent task to manager connections and data processing ## Part 2 : main workflow 1. ESP32 would play the role of TCP Server 2. TCP Client[we choose ubuntu platform] would connect and send JSON formatted data to ESP32 3. ESP32 would parse JSON data and respond to TCP Client ## Part 3 : how to make it run Step 1: config ESP32 - config WiFi SSID and WiFi Password - config default serial port - config baud rate[optional] Step 2: build sample and run TCP Server ``` $ make flash monitor ``` Step 3: compile the TCP Client ``` $gcc client.c ``` Step 4: send JSON data by TCP Client ``` ./a.out "192.168.111.108" "{\"sample_para\":{\"value\":\"1\"}}" ``` **notes that IP address is the same with ESP32 got, we could see it when tcp server started** ## Part 4 : Notes about the sample 1. you should run hello-world example OK before you start this sample 2. there care about 4 Bytes JSON-length information in front of TCP data stream 3. respond to TCP Client not using JSON formatted data based on simplify TCP Client parse process consideration