UDP通讯测试

参考资料：UNIX网络编程

实验平台：PC为client，RaspberryPi为server

基本类型和接口函数，参考man手册

    #include <sys/socket.h>struct sockaddr {sa_family_t     sa_family;      /* Address family */char            sa_data[];      /* Socket address */};#include <netinet/in.h>struct sockaddr_in {sa_family_t     sin_family;     /* AF_INET */in_port_t       sin_port;       /* Port number */struct in_addr  sin_addr;       /* IPv4 address */};struct in_addr {in_addr_t s_addr;};typedef uint32_t in_addr_t;typedef uint16_t in_port_t;#include <sys/socket.h>ssize_t sendto(int sockfd, const void buf[.len], size_t len, int flags,const struct sockaddr *dest_addr,socklen_t addrlen);ssize_t recvfrom(int