完成了第 8 章 域名及网络地址

ch08/gethostbyaddr.c

@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+void error_handling(char *message);
+
+int main(int argc, char *argv[])
+{
+    int i;
+    struct hostent *host;
+    struct sockaddr_in addr;
+    if (argc != 2)
+    {
+        printf("Usage : %s <IP>\n", argv[0]);
+        exit(1);
+    }
+
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_addr.s_addr = inet_addr(argv[1]);
+    host = gethostbyaddr((char *)&addr.sin_addr, 4, AF_INET);
+    if (!host)
+        error_handling("gethost... error");
+
+    printf("Official name: %s \n", host->h_name);
+    for (i = 0; host->h_aliases[i]; i++)
+        printf("Aliases %d:%s \n", i + 1, host->h_aliases[i]);
+    printf("Address type: %s \n",
+           (host->h_addrtype == AF_INET) ? "AF_INET" : "AF_INET6");
+
+    for (i = 0; host->h_addr_list[i]; i++)
+        printf("IP addr %d: %s \n", i + 1,
+               inet_ntoa(*(struct in_addr *)host->h_addr_list[i]));
+
+    return 0;
+}
+void error_handling(char *message)
+{
+    fputs(message, stderr);
+    fputc('\n', stderr);
+    exit(1);
+}