FreeCoap Trial of CoAP Protocol Open Source Code

1. FreeCoAP

• FreeCoAP
  • Development language: C
  • Function: Client + Server + HTTP/CoAP Proxy
  • 模块： Core, DTLS, Blockwise Transfers
  • Open source agreement: BSD
  • Download link: https://github.com/keith-cullen/FreeCoAP ]( https://github.com/keith-cullen/FreeCoAP )
  • Support platform: Linux (gnulinux)

2. Source Code Directory

├── build-aux
├── certs
├── docs
├── lib
│   ├── include
│   └── src
├── proxy
│   ├── common
│   │   ├── include
│   │   └── src
│   └── http_coap
│       ├── include
│       └── src
├── sample
│   ├── reg_client
│   ├── reg_server
│   ├── time_client
│   └── time_server
└── test
    ├── test_coap_client
    ├── test_coap_mem
    ├── test_coap_msg
    ├── test_coap_server
    ├── test_config
    ├── test_cross
    ├── test_data_buf
    ├── test_http_client
    ├── test_http_msg
    ├── test_lock
    ├── test_proxy_http_coap
    ├── test_thread
    ├── test_tls_client
    ├── test_tls_server
    └── test_uri

3. Compile

• Create installation script

  cd /home/xxx/work/coap/FreeCoAP-master
  autoreconf --install
  

• Compile

  • Install gnutls in CentOs7

    yum install gnutls*  # 注意: 编译时，源代码中有include <gnutls/x509.h>，因此，还需要安装gnutls-develop
    # 或安装
    yum install gnutls-develop
    # 查看头文件
    ls /usr/include/gnutls/x509.h
    /usr/include/gnutls/x509.h 
    # 创建libgnutls.so的软链接
    cd /lib
    ln -s /usr/lib64/libgnutls.so.28.43.3 libgnutls.so
    

  • Compile libfreecoap.so

    cd /home/xxx/work/coap/FreeCoAP-master
    mkdir bin
    ./configure --prefix=/home/xxx/work/coap/FreeCoAP-master/bin
    make
    make install
    # 查看输出
    ll /home/xxx/work/coap/FreeCoAP-master/bin/lib/
    -rw-r--r--. 1 root root 268930 4月  22 11:52 libfreecoap.a
    -rwxr-xr-x. 1 root root    988 4月  22 11:52 libfreecoap.la
    lrwxrwxrwx. 1 root root     20 4月  22 11:52 libfreecoap.so -> libfreecoap.so.0.0.5
    lrwxrwxrwx. 1 root root     20 4月  22 11:52 libfreecoap.so.0 -> libfreecoap.so.0.0.5
    -rwxr-xr-x. 1 root root 181304 4月  22 11:52 libfreecoap.so.0.0.5
    

    note: The FreeCoAP library built using this process requires GnuTLS and cannot be used without DTLS (编译依赖需要gnutls库，生成的freecoap库没有dtls不能使用)

• Routine

  • Time server and client based on CoAP/IPv4

    $ cd FreeCoAP/sample/time_server
    $ make dtls=n
    $ ./time_server 0.0.0.0 10000
    (In a different terminal)
    $ cd FreeCoAP/sample/time_client
    $ make dtls=n
    $ ./time_client 127.0.0.1 10000
    

  • Time server and client based on CoAP/DTLS/IPv4

    $ cd FreeCoAP/sample/time_server
    $ make
    $ ./time_server 0.0.0.0 10000
    (In a different terminal)
    $ cd FreeCoAP/sample/time_client
    $ make
    $ ./time_client 127.0.0.1 10000
    

4. Test (time server/client)

• Throughput rate of server and client

  Environment: CentOS 7 64bit, PC, Intel® Core™ i3-6100 CPU @ 3.70GHz

  • 100,000 consecutive requests, 41254.12 times / s
  • 500,000 consecutive requests, 36922.16 times / s

• Problems found in the test

  • Comment out in main.c of time_client

    ret = time_client_get_time(&client, buf, sizeof(buf));
    if (ret < 0)
    {
            
            
      ...
    }
    /* sleep(1); */
    

    Communication is interrupted and "Bad message" error is reported. Debug, the source of the error report is in the coap_client_exchange_con function of coap_client.c

    static int coap_client_exchange_con(coap_client_t *client, coap_msg_t *req, coap_msg_t *resp)
    {
            
            
     ssize_t num = 0;
     int ret = 0;
    
    /*  wait for piggy-backed response in ack message
     *  or ack message and separate response message
    */
    coap_log_info("Expecting acknowledgement from host %s and port %s", client->server_host, client->server_port);
    coap_client_start_ack_timer(client);
    while (1)
    {
            
            
        ret = coap_client_listen_ack(client, req);
        ...
        if (coap_msg_get_msg_id(resp) == coap_msg_get_msg_id(req))
        {
            
            
            if (coap_msg_get_type(resp) == COAP_MSG_ACK)
            {
            
            
                if (coap_msg_is_empty(resp))
                {
            
            
                    /* received ack message, wait for separate response message */
                    coap_log_info("Received acknowledgement from host %s and port %s", client->server_host, client->server_port);
                    return coap_client_exchange_sep(client, req, resp);
                }
                else if (coap_client_match_token(req, resp)) /* 错误发生地: token不等 */
                {
            
            
                    return coap_client_handle_piggybacked_response(client, resp);
                }
            }
            else if (coap_msg_get_type(resp) == COAP_MSG_RST)
            {
            
            
                return -ECONNRESET;
            }
            coap_client_reject(client, resp);
            /* 错误报告地: Bad message */
            return -EBADMSG;
        }
        else if (coap_client_match_token(req, resp))
    

    As mentioned above, the root cause should be caused by not updating the token when the server responds to ack, and it is under debugging...