How do C++ functions handle DNS queries in network programming?
Apr 27, 2024 pm 06:39 PMC The standard library provides functions to handle DNS queries in network programming: gethostbyname(): Find host information based on the host name. gethostbyaddr(): Find host information based on IP address. dns_lookup(): Asynchronously resolve DNS.
C function DNS query processing in network programming
In network programming, the Domain Name System (DNS) is crucial for resolving domain names into IP addresses important. The C standard library provides powerful functions to simplify this process.
Function introduction
The functions used for DNS query in the C standard library include:
-
gethostbyname()
: Find the host based on the host name information. -
gethostbyaddr()
: Find host information based on IP address. -
dns_lookup()
: Asynchronously resolve DNS based on hostname or IP address.
Practical case
Suppose we want to obtain the IP address of www.google.com
and display the results. Here is a code example using gethostbyname()
:
#include <netdb.h> #include <iostream> int main() { // 獲取主機(jī)名 std::string hostname = "www.google.com"; // 獲取主機(jī)信息 struct hostent *host = gethostbyname(hostname.c_str()); // 檢查是否有錯(cuò)誤 if (!host) { std::cerr << "gethostbyname() failed" << std::endl; return EXIT_FAILURE; } // 輸出 IP 地址 std::cout << "IP 地址:" << host->h_addr_list[0] << std::endl; return EXIT_SUCCESS; }
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