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81 lines
2.9 KiB
Markdown
81 lines
2.9 KiB
Markdown
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# CoAP client example
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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this CoAP client example is adaptation of one of the [libcoap](https://github.com/obgm/libcoap) example.
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CoAP client example would connect your ESP32 device to any CoAP server, fetch data from CoAP server and upstream data to CoAP server.
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The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained networks in the Internet of Things.
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The protocol is designed for machine-to-machine (M2M) applications such as smart energy and building automation.
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please refer to [RFC7252](https://www.rfc-editor.org/rfc/pdfrfc/rfc7252.txt.pdf) for more details.
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## How to use example
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### Configure the project
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```
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idf.py menuconfig
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```
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* Set serial port under Serial Flasher config
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* Set Target Uri under Example Configuration
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* Set WiFi SSID under Example Configuration
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* Set WiFi Password under Example Configuration
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### Build and Flash
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Build the project and flash it to the board, then run monitor tool to view serial output:
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```
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idf.py -p PORT flash monitor
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```
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
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## Example Output
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Prerequisite: we startup a CoAP server on coap server example,
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or use the default of coap://californium.eclipse.org.
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and you could receive data from CoAP server if succeed,
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such as the following log:
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```
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...
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I (332) wifi: mode : sta (30:ae:a4:04:1b:7c)
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I (1672) wifi: n:11 0, o:1 0, ap:255 255, sta:11 0, prof:1
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I (1672) wifi: state: init -> auth (b0)
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I (1682) wifi: state: auth -> assoc (0)
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I (1692) wifi: state: assoc -> run (10)
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I (1692) wifi: connected with huawei_cw, channel 11
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I (1692) wifi: pm start, type: 1
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I (2582) event: sta ip: 192.168.3.89, mask: 255.255.255.0, gw: 192.168.3.1
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I (2582) CoAP_client: Connected to AP
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I (2582) CoAP_client: DNS lookup succeeded. IP=104.196.15.150
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Received:
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************************************************************
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CoAP RFC 7252 Cf 2.0.0-SNAPSHOT
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************************************************************
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This server is using the Eclipse Californium (Cf) CoAP framework
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published under EPL+EDL: http://www.eclipse.org/californium/
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(c) 2014, 2015, 2016 Institute for Pervasive Computing, ETH Zurich and others
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************************************************************
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...
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```
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## libcoap Documentation
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This can be found at https://libcoap.net/doc/reference/4.2.0/
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## Troubleshooting
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* Please make sure Target Url includes valid `host`, optional `port`, optional `path`, and begins
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with `coap://` or `coap+tcp://` for a coap server that supports TCP
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(not all do including coap+tcp://californium.eclipse.org).
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* libcoap logging can be increased by changing `#define COAP_LOGGING_LEVEL 0`
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to `#define COAP_LOGGING_LEVEL 9`
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