POCO库中文编程参考指南（9）Poco::Net::DNS

1 Poco::Net::DNS

namespace Poco {
namespace Net {
class Net_API DNS {
public:
    static HostEntry hostByName(const std::string& hostname);
    static HostEntry hostByAddress(const IPAddress& address);
    static HostEntry resolve(const std::string& address);
    static IPAddress resolveOne(const std::string& address);
    static HostEntry thisHost();
    static std::string hostName();
};
}
}

HostEntry 中存储 host primary name（canonical name）、alias name list、IP address list。

2 相关 API

得到一个 HostEntry 实例：

const HostEntry& entry = DNS::hostByName("google.com");

输出域名：

std::cout << entry.name() << std::endl;

Address 和 Alias：

const HostEntry::AliasList& aliases = entry.aliases();
const HostEntry::AddressList& addrs = entry.addresses();

3 Source code

POCO 的官方文档中的 Sample 有错误，以下提供一个正确的示例，其中域名是通过参数传入的。

#include "Poco/Net/DNS.h"
#include <iostream>
using Poco::Net::DNS;
using Poco::Net::IPAddress;
using Poco::Net::HostEntry;
int main(int argc, char** argv)
{
    if (argc != 2) {
        std::cout << "Invalid argument number." << std::endl;
    }
    const HostEntry& entry = DNS::hostByName(argv[1]);
    std::cout << "Canonical Name: " << entry.name() << std::endl;

    const HostEntry::AliasList& aliases = entry.aliases();
    for (HostEntry::AliasList::const_iterator it = aliases.begin();
        it !=   aliases.end(); ++it)
        std::cout << "Alias: " << *it << std::endl;

    const HostEntry::AddressList& addrs = entry.addresses();
    for (HostEntry::AddressList::const_iterator it = addrs.begin();
        it !=   addrs.end(); ++it)
        std::cout << "Address: " << it->toString() << std::endl;

    return 0;
}

编译：

$ g++ name_solver.cpp -o name_solver \
-I/usr/local/include -I/usr/local/lib -lPocoNet

运行：

$ ./name_solver baidu.com
Canonical Name: baidu.com
Address: 123.125.114.144
Address: 123.125.114.144
Address: 220.181.111.85
Address: 220.181.111.85
Address: 220.181.111.86
Address: 220.181.111.86

$ ./name_solver www.ustc.edu.cn
Canonical Name: ustc.edu.cn
Address: 202.38.64.246
Address: 202.38.64.246