libcoap在Ubuntu下的编译（基于CMake）

引言

libcoap 是一个开源的轻量级 C 语言库，用于实现 CoAP（Constrained Application Protocol，受限应用协议）。CoAP 是一种专为资源受限设备设计的轻量级通信协议，适用于物联网（IoT）和嵌入式系统。今天介绍一下如何在Linux下进行编译。

libcoap主要功能和特点

协议实现：libcoap 完整实现了 CoAP 协议的 RFC 7252 标准。
客户端和服务器支持：提供了 CoAP 客户端和服务器功能，可用于开发基于 CoAP 的应用程序。
跨平台支持：支持多种操作系统，包括 Linux、Windows、iOS 和 Android。
安全特性：支持 DTLS（Datagram Transport Layer Security）等安全机制。
RESTful 风格：支持 RESTful 架构，提供 GET、POST、PUT 和 DELETE 等基本方法。
低资源消耗：专为资源受限的设备设计，优化了数据报长度和通信效率。

编译

官方和网上很多教程都是基于configure系统进行编译的，比较麻烦。今天介绍一下如何用CMake进行编译。

首先使用Git获得源码：

git clone https://github.com/obgm/libcoap.git

如果想使用SSL功能，需要先安装OpenSSL，我们此次只是在本地测试，就禁用了SSL相关功能，在命令行加上-DENABLE_DTLS=OFF。

armdev@armdev-VirtualBox:~/coap/libcoap-4.3.5$ cmake . -DENABLE_DTLS=OFF
-- The CXX compiler identification is GNU 7.5.0
-- The C compiler identification is GNU 7.5.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Looking for assert.h
-- Looking for assert.h - found
-- Looking for string.h
-- Looking for string.h - found
-- Looking for strings.h
-- Looking for strings.h - found
-- Looking for byteswap.h
-- Looking for byteswap.h - found
-- Looking for inttypes.h
-- Looking for inttypes.h - found
-- Looking for errno.h
-- Looking for errno.h - found
-- Looking for limits.h
-- Looking for limits.h - found
-- Looking for memory.h
-- Looking for memory.h - found
-- Looking for sys/sysctl.h
-- Looking for sys/sysctl.h - found
-- Looking for net/if.h
-- Looking for net/if.h - found
-- Looking for ifaddrs.h
-- Looking for ifaddrs.h - found
-- Looking for netinet/in.h
-- Looking for netinet/in.h - found
-- Looking for sys/epoll.h
-- Looking for sys/epoll.h - found
-- Looking for sys/timerfd.h
-- Looking for sys/timerfd.h - found
-- Looking for arpa/inet.h
-- Looking for arpa/inet.h - found
-- Looking for stdbool.h
-- Looking for stdbool.h - found
-- Looking for netdb.h
-- Looking for netdb.h - found
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Looking for stdlib.h
-- Looking for stdlib.h - found
-- Looking for stdint.h
-- Looking for stdint.h - found
-- Looking for sys/ioctl.h
-- Looking for sys/ioctl.h - found
-- Looking for sys/socket.h
-- Looking for sys/socket.h - found
-- Looking for sys/stat.h
-- Looking for sys/stat.h - found
-- Looking for sys/time.h
-- Looking for sys/time.h - found
-- Looking for sys/types.h
-- Looking for sys/types.h - found
-- Looking for sys/unistd.h
-- Looking for sys/unistd.h - found
-- Looking for time.h
-- Looking for time.h - found
-- Looking for unistd.h
-- Looking for unistd.h - found
-- Looking for float.h
-- Looking for float.h - found
-- Looking for stddef.h
-- Looking for stddef.h - found
-- Looking for winsock2.h
-- Looking for winsock2.h - not found
-- Looking for ws2tcpip.h
-- Looking for ws2tcpip.h - not found
-- Looking for malloc
-- Looking for malloc - found
-- Looking for memset
-- Looking for memset - found
-- Looking for select
-- Looking for select - found
-- Looking for socket
-- Looking for socket - found
-- Looking for strcasecmp
-- Looking for strcasecmp - found
-- Looking for pthread_mutex_lock
-- Looking for pthread_mutex_lock - found
-- Looking for getaddrinfo
-- Looking for getaddrinfo - found
-- Looking for strnlen
-- Looking for strnlen - found
-- Looking for strrchr
-- Looking for strrchr - found
-- Looking for getrandom
-- Looking for getrandom - found
-- Looking for random
-- Looking for random - found
-- Looking for if_nametoindex
-- Looking for if_nametoindex - found
-- Looking for CMSG_FIRSTHDR
-- Looking for CMSG_FIRSTHDR - found
-- compiling with client support
-- compiling with server support
-- compiling with proxy support
-- compiling with OSCORE support
-- compiling with WebSockets support
-- compiling with async separate response support
-- compiling with IPv4 support
-- compiling with IPv6 support
-- compiling with Unix socket support
-- compiling with Q-Block (RFC9177) support
-- compiling with observe persistence support
-- compiling with epoll support
-- compiling with thread safe support
-- compiling with max logging level set to 8
-- 
-- libcoap Configuration Summary:
-- 
-- PACKAGE VERSION..................4.3.5
-- PACKAGE SOURCE...................4.3.5
-- LIBRARY API VERSION..............3
-- LIBRARY ABI VERSION..............3.2.0
-- ENABLE_DTLS:.....................OFF
-- ENABLE_TCP:......................ON
-- ENABLE_IPV4:.....................ON
-- ENABLE_IPV6:.....................ON
-- ENABLE_AF_UNIX:..................ON
-- ENABLE_WEBSOCKETS:...............ON
-- ENABLE_Q_BLOCK:..................ON
-- ENABLE_CLIENT_MODE:..............ON
-- ENABLE_SERVER_MODE:..............ON
-- ENABLE_OSCORE:...................ON
-- ENABLE_ASYNC:....................ON
-- ENABLE_THREAD_SAFE:..............ON
-- ENABLE_THREAD_RECURSIVE_CHECK....OFF
-- ENABLE_DOCS:.....................ON
-- ENABLE_EXAMPLES:.................ON
-- DTLS_BACKEND:....................default
-- WITH_GNUTLS:.....................OFF
-- WITH_TINYDTLS:...................OFF
-- WITH_OPENSSL:....................OFF
-- WITH_WOLFSSL:....................OFF
-- WITH_MBEDTLS:....................OFF
-- HAVE_LIBTINYDTLS:................
-- HAVE_LIBGNUTLS:..................
-- HAVE_LIBOPENSSL:.................
-- HAVE_LIBWOLFSSL:.................
-- HAVE_LIBMBEDTLS:.................
-- WITH_EPOLL:......................ON
-- WITH_OBSERVE_PERSIST:............ON
-- BUILD_SHARED_LIBS:...............OFF
-- MAX_LOGGING_LEVEL:...............8
-- WARNING_TO_ERROR:................OFF
-- CMAKE_C_COMPILER:................/usr/bin/cc
-- CMAKE_CXX_COMPILER_ID:...........GNU
-- CMAKE_BUILD_TYPE:................Debug
-- CMAKE_SYSTEM_PROCESSOR:..........x86_64
-- CMAKE_HOST_SYSTEM_NAME:..........Linux
-- CMAKE_GENERATOR:.................Unix Makefiles
-- 
-- Could NOT find Doxygen (missing: DOXYGEN_EXECUTABLE) 
CMake Warning at CMakeLists.txt:945 (message):Doxygen need to be installed to generate the doxygen documentation-- Configuring done
-- Generating done
-- Build files have been written to: /home/armdev/coap/libcoap-4.3.5

这里提示因为没有Doxygen而报错，可以忽略。

然后使用make命令进行编译。

armdev@armdev-VirtualBox:~/coap/libcoap-4.3.5$ make
Consolidate compiler generated dependencies of target coap-3
[  2%] Building C object CMakeFiles/coap-3.dir/src/coap_address.c.o
[  4%] Building C object CMakeFiles/coap-3.dir/src/coap_asn1.c.o
[  6%] Building C object CMakeFiles/coap-3.dir/src/coap_async.c.o
[  8%] Building C object CMakeFiles/coap-3.dir/src/coap_block.c.o
[ 10%] Building C object CMakeFiles/coap-3.dir/src/coap_cache.c.o
[ 12%] Building C object CMakeFiles/coap-3.dir/src/coap_debug.c.o
[ 14%] Building C object CMakeFiles/coap-3.dir/src/coap_dtls.c.o
[ 16%] Building C object CMakeFiles/coap-3.dir/src/coap_encode.c.o
[ 18%] Building C object CMakeFiles/coap-3.dir/src/coap_event.c.o
[ 20%] Building C object CMakeFiles/coap-3.dir/src/coap_hashkey.c.o
[ 22%] Building C object CMakeFiles/coap-3.dir/src/coap_io.c.o
[ 24%] Building C object CMakeFiles/coap-3.dir/src/coap_layers.c.o
[ 26%] Building C object CMakeFiles/coap-3.dir/src/coap_mem.c.o
[ 28%] Building C object CMakeFiles/coap-3.dir/src/coap_net.c.o
[ 30%] Building C object CMakeFiles/coap-3.dir/src/coap_netif.c.o
[ 32%] Building C object CMakeFiles/coap-3.dir/src/coap_notls.c.o
[ 34%] Building C object CMakeFiles/coap-3.dir/src/coap_option.c.o
[ 36%] Building C object CMakeFiles/coap-3.dir/src/coap_oscore.c.o
[ 38%] Building C object CMakeFiles/coap-3.dir/src/coap_pdu.c.o
[ 40%] Building C object CMakeFiles/coap-3.dir/src/coap_prng.c.o
[ 42%] Building C object CMakeFiles/coap-3.dir/src/coap_proxy.c.o
[ 44%] Building C object CMakeFiles/coap-3.dir/src/coap_resource.c.o
[ 46%] Building C object CMakeFiles/coap-3.dir/src/coap_session.c.o
[ 48%] Building C object CMakeFiles/coap-3.dir/src/coap_sha1.c.o
[ 51%] Building C object CMakeFiles/coap-3.dir/src/coap_str.c.o
[ 53%] Building C object CMakeFiles/coap-3.dir/src/coap_subscribe.c.o
[ 55%] Building C object CMakeFiles/coap-3.dir/src/coap_tcp.c.o
[ 57%] Building C object CMakeFiles/coap-3.dir/src/coap_threadsafe.c.o
[ 59%] Building C object CMakeFiles/coap-3.dir/src/coap_time.c.o
[ 61%] Building C object CMakeFiles/coap-3.dir/src/coap_uri.c.o
[ 63%] Building C object CMakeFiles/coap-3.dir/src/coap_ws.c.o
[ 65%] Building C object CMakeFiles/coap-3.dir/src/oscore/oscore.c.o
[ 67%] Building C object CMakeFiles/coap-3.dir/src/oscore/oscore_cbor.c.o
[ 69%] Building C object CMakeFiles/coap-3.dir/src/oscore/oscore_context.c.o
[ 71%] Building C object CMakeFiles/coap-3.dir/src/oscore/oscore_cose.c.o
[ 73%] Building C object CMakeFiles/coap-3.dir/src/oscore/oscore_crypto.c.o
[ 75%] Linking C static library libcoap-3.a
[ 75%] Built target coap-3
[ 77%] Building C object CMakeFiles/coap-rd.dir/examples/coap-rd.c.o
[ 79%] Linking C executable coap-rd
[ 79%] Built target coap-rd
[ 81%] Building C object CMakeFiles/coap-client.dir/examples/coap-client.c.o
[ 83%] Linking C executable coap-client
[ 83%] Built target coap-client
[ 85%] Building C object CMakeFiles/etsi_iot_01.dir/examples/etsi_iot_01.c.o
[ 87%] Linking C executable etsi_iot_01
[ 87%] Built target etsi_iot_01
[ 89%] Building C object CMakeFiles/oscore-interop-server.dir/examples/oscore-interop-server.c.o
[ 91%] Linking C executable oscore-interop-server
[ 91%] Built target oscore-interop-server
[ 93%] Building C object CMakeFiles/tiny.dir/examples/tiny.c.o
[ 95%] Linking C executable tiny
[ 95%] Built target tiny
[ 97%] Building C object CMakeFiles/coap-server.dir/examples/coap-server.c.o
[100%] Linking C executable coap-server
[100%] Built target coap-server

编译成功后，在当前目录可以看到libcoap-3.a文件和两个例子的可执行文件。

直接运行一下coap-client说明编译正确。

运行测试程序

首先运行./coap-server启动服务端。

然后运行客户端程序访问服务端：

armdev@armdev-VirtualBox:~/coap/libcoap-4.3.5$ ./coap-client -m get coap://localhost/
This is a test server made with libcoap (see https://libcoap.net)
Copyright (C) 2010--2024 Olaf Bergmann <bergmann@tzi.org> and others