获取本地IP地址

首先来一种windows和linux平台都支持的

#ifdef WIN32
#include <boost/asio.hpp>
#include <boost/asio/io_service.hpp>
#else
#include <stdio.h>
#include <sys/types.h>
#include <ifaddrs.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#endif

std::string getLocalIpAddress(const std::string &slash) {
		static bool s_once = true;
		static std::string s_result;

		if (s_once) {
			s_once = false;
#ifdef WIN32
			using boost::asio::ip::tcp;
			try {
				boost::asio::io_service io_service;
				tcp::resolver resolver(io_service);
				tcp::resolver::query query(tcp::v4(), boost::asio::ip::host_name(), "");
				tcp::resolver::iterator iter = resolver.resolve(query);
				tcp::resolver::iterator end; // End marker.
				while (iter != end) {
					tcp::endpoint ep = *iter++;
					if (!s_result.empty()) {
						s_result += slash;
					}
					s_result += ep.address().to_string();
				}
			}
			catch (std::exception &e) {
				std::cerr << "get local ip address failed, " << e.what() << std::endl;
			}
#else
			struct ifaddrs * ifAddrStruct = NULL;
			struct ifaddrs * ifa = NULL;
			void * tmpAddrPtr = NULL;

			getifaddrs(&ifAddrStruct);
			for (ifa = ifAddrStruct; ifa != NULL; ifa = ifa->ifa_next) {
				if (!ifa->ifa_addr) {
					continue;
				}
				if (ifa->ifa_addr->sa_family == AF_INET) { // check it is IP4
														   // is a valid IP4 Address
					tmpAddrPtr = &((struct sockaddr_in *)ifa->ifa_addr)->sin_addr;
					char addressBuffer[INET_ADDRSTRLEN];
					inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN);
					std::string address(addressBuffer);
					if (address != "127.0.0.1") {
						if (!s_result.empty()) {
							s_result += slash;
						}
						s_result += address;
					}
				}
			}
			if (ifAddrStruct != NULL) freeifaddrs(ifAddrStruct);
#endif
		}
		return s_result;
	}

再来看一下Qt的写法，看起来清爽多了

	QString getLocalHost()
	{
		QStringList ipList;
		const QHostAddress &localhost = QHostAddress(QHostAddress::LocalHost);
		for (const QHostAddress &address : QNetworkInterface::allAddresses()) {
			if (address.protocol() == QAbstractSocket::IPv4Protocol && address != localhost)
			ipList << address.toString();
		}
		return ipList.join("-");
	}