C++ IPv4与IPv6的兼容编码

这里不再对IPv6 socket相关编程的基础知识进行讲解，只提供一个IP协议无关的服务端和客户端的代码，仅供参考。

服务端代码：

#include <iostream>



#include <string>



#include <sys/types.h>



#include <sys/socket.h>



#include <arpa/inet.h>



#include <netdb.h>



#include <errno.h>



#include <time.h>



 




using namespace std;



 



int tcp_listen(const char *host, const char *service, const int listen_num = 5)



{



	int listenfd, ret;



	const int on = 1;



	struct addrinfo hints, *res, *ressave;




	bzero(&hints, sizeof(hints));



	hints.ai_flags = AI_PASSIVE;



	hints.ai_family = AF_UNSPEC;



	hints.ai_socktype = SOCK_STREAM;



	hints.ai_protocol = IPPROTO_IP;



 



	if (0 != (ret = getaddrinfo(host, service, &hints, &res)))



	{



		cout << "getaddrinfo error: " << gai_strerror(ret) << endl;



		return -1;



	}



 



	ressave = res;



	while(NULL != res)



	{



		if (-1 == (listenfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol)))



		{



			cout << "create socket error: " << strerror(errno) << endl;



			res = res->ai_next;



			continue;



		}



 



		if (-1 == setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)))



		{



			cout << "setsockopt error: " << strerror(errno) << endl;



			close(listenfd);



			res = res->ai_next;



			continue;



		}



 



		if (-1 == bind(listenfd, res->ai_addr, res->ai_addrlen))



		{



			cout << "bind error: " << strerror(errno) << endl;



                        close(listenfd);



                        res = res->ai_next;



                        continue;



		}



 



		if (-1 == listen(listenfd, listen_num))



		{



			cout << "listen error: " << strerror(errno) << endl;



                        close(listenfd);



                        res = res->ai_next;



                        continue;



		}



 



		break;



	}



 



	freeaddrinfo(ressave);



 



	if (NULL == res)



		return -1;



 



	return listenfd;



}



 



int get_addrinfo(const struct sockaddr *addr, string &ip, in_port_t &port)



{



	void *numeric_addr = NULL;



	char addr_buff[INET6_ADDRSTRLEN];



 



	if (AF_INET == addr->sa_family)



	{



		numeric_addr = &((struct sockaddr_in*)addr)->sin_addr;



		port = ntohs(((struct sockaddr_in*)addr)->sin_port);



	}



	else if (AF_INET6 == addr->sa_family)



	{



		numeric_addr = &((struct sockaddr_in6*)addr)->sin6_addr;



		port = ntohs(((struct sockaddr_in6*)addr)->sin6_port);



	}



	else




	{



		return -1;



	}



 



	if (NULL != inet_ntop(addr->sa_family, numeric_addr, addr_buff, sizeof(addr_buff)))



		ip = addr_buff;



	else




		return -1;



 



	return 0;



}



 



int main(int argc, char *argv[])



{



	int listenfd, connfd;



	struct sockaddr_storage cliaddr;




	socklen_t len = sizeof(cliaddr);



	time_t now;



	char buff[128];



 



	if (2 == argc) //指定端口




		listenfd = tcp_listen(NULL, argv[1]);



	else if (3 == argc) //指定本地IP和端口




		listenfd = tcp_listen(argv[1], argv[2]);



	else




	{



                cout << "usage: " << argv[0] << " [<hostname/ipaddress>] <service/port>" << endl;



		return -1;



	}



 



	if (listenfd < 0)



	{



		cout << "call tcp_listen error" << endl;



		return -1;



	}



 



	while (true)



	{



		connfd = accept(listenfd, (struct sockaddr*)&cliaddr, &len);



 



		string ip = "";



		in_port_t port = 0;



		get_addrinfo((struct sockaddr*)&cliaddr, ip, port);



		cout << "client " << ip << "|" << port << " login" << endl;



 



		now = time(NULL);



		snprintf(buff, sizeof(buff) - 1, "%.24s", ctime(&now));



		write(connfd, buff, strlen(buff));



		close(connfd);



	}



 



	close(listenfd);



	return 0;



}

客户端代码：

#include <iostream>



#include <string>



#include <sys/types.h>



#include <sys/socket.h>



#include <arpa/inet.h>



#include <netdb.h>



#include <errno.h>



#include <time.h>



 




using namespace std;



 



int tcp_connect(const char *host, const char *service)



{



	int sockfd, ret;



	struct addrinfo hints, *res, *ressave;




	bzero(&hints, sizeof(hints));



	hints.ai_family = AF_UNSPEC;



	hints.ai_socktype = SOCK_STREAM;



	hints.ai_protocol = IPPROTO_IP;



 



	if (0 != (ret = getaddrinfo(host, service, &hints, &res)))



	{



		cout << "getaddrinfo error: " << gai_strerror(ret) << endl;



		return -1;



	}



 



	ressave = res;



	while (NULL != res)



	{



		if (-1 == (sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol)))



                {



                        cout << "create socket error: " << strerror(errno) << endl;



                        res = res->ai_next;



                        continue;



                }



 



		if (-1 == connect(sockfd, res->ai_addr, res->ai_addrlen))



		{



			cout << "connect error: " << strerror(errno) << endl;



                        close(sockfd);



			res = res->ai_next;



                        continue;



		}



 



		break;



	}



	



	freeaddrinfo(ressave);



 



	if (NULL == res)



		return -1;



 



	return sockfd;



}



 



int main(int argc, char *argv[])



{



	int sockfd, n;



	char buff[128];



	struct sockaddr_storage cliaddr;




	



	if (3 != argc)



	{



		cout << "usage: " << argv[0] << " <hostname/ipaddress> <service/port>" << endl;



		return -1;



	}



 



	sockfd = tcp_connect(argv[1], argv[2]);



	if (sockfd < 0)



	{



		cout << "call tcp_connect error" << endl;



		return -1;



	}



 



	bzero(buff, sizeof(buff));



	while ((n = read(sockfd, buff, sizeof(buff) - 1) > 0))



	{



		cout << buff << endl;



		bzero(buff, sizeof(buff));



	}



	close(sockfd);



 



	return 0;



}

编译：

g++ daytimesrv.cpp -o daytimesrv

g++ daytimecli.cpp -o daytimecli

运行举例:

服务端运行情况：

客户端运行情况：

以上客户端的请求与服务端的输出一一对应，客户端可以尝试用不同的IP去连接，然后观察服务端的输出，有助于理解底层的交互过程。来源：https://blog.****.net/ligt0610/article/details/18667595#