IN_ADDR hostIP;
char *host;
HOSTENT *hostName;
host = inet_ntoa(hostIP);//as hostIP = "192.168.112.1"
hostName = gethostbyaddr(host,sizeof(host),AF_INET);
这样写对吗？
char *host;
HOSTENT *hostName;
host = inet_ntoa(hostIP);//as hostIP = "192.168.112.1"
hostName = gethostbyaddr(host,sizeof(host),AF_INET);
这样写对吗？
Platform SDK: Windows Sockets
IPv4-only Client Code
[This is preliminary documentation and subject to change.] The following code is the Simplec.c file, which is an IPv4-only Windows Sockets client (an IPv6 enabled version of the Simplec.c file can be found in Appendix B). This code is provided for comparison purposes only—use Appendix B for an example of how to write an IPv6-enabled client./******************************************************************************* simplec.c - Simple TCP/UDP client using Winsock 1.1
*
* This is a part of the Microsoft Source Code Samples.
* Copyright 1996 - 2000 Microsoft Corporation.
* All rights reserved.
* This source code is only intended as a supplement to
* Microsoft Development Tools and/or WinHelp documentation.
* See these sources for detailed information regarding the
* Microsoft samples programs.
\******************************************************************************/#define WIN32_LEAN_AND_MEAN
#include <winsock2.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>#define DEFAULT_PORT 5001
#define DEFAULT_PROTO SOCK_STREAM // TCPvoid Usage(char *progname) {
fprintf(stderr,"Usage\n%s -p [protocol] -n [server] -e [endpoint] -l [iterations]\n",
progname);
fprintf(stderr,"Where:\n\tprotocol is one of TCP or UDP\n");
fprintf(stderr,"\tserver is the IP address or name of server\n");
fprintf(stderr,"\tendpoint is the port to listen on\n");
fprintf(stderr,"\titerations is the number of loops to execute\n");
fprintf(stderr,"\t(-l by itself makes client run in an infinite loop,");
fprintf(stderr," Hit Ctrl-C to terminate it)\n");
fprintf(stderr,"Defaults are TCP , localhost and 5001\n");
WSACleanup();
exit(1);
}
int main(int argc, char **argv) { char Buffer[128];
char *server_name= "localhost";
unsigned short port = DEFAULT_PORT;
int retval, loopflag=0;
int i, loopcount,maxloop=-1;
unsigned int addr;
int socket_type = DEFAULT_PROTO;
struct sockaddr_in server;
struct hostent *hp;
WSADATA wsaData;
SOCKET conn_socket; if (argc >1) {
for(i=1;i <argc;i++) {
if ( (argv[i][0] == '-') || (argv[i][0] == '/') ) {
switch(tolower(argv[i][1])) {
case 'p':
if (!stricmp(argv[i+1], "TCP") )
socket_type = SOCK_STREAM;
else if (!stricmp(argv[i+1], "UDP") )
socket_type = SOCK_DGRAM;
else
Usage(argv[0]);
i++;
break; case 'n':
server_name = argv[++i];
break;
case 'e':
port = atoi(argv[++i]);
break;
case 'l':
loopflag =1;
if (argv[i+1]) {
if (argv[i+1][0] != '-')
maxloop = atoi(argv[i+1]);
}
else
maxloop = -1;
i++;
break;
default:
Usage(argv[0]);
break;
}
}
else
Usage(argv[0]);
}
}
if ((retval = WSAStartup(0x202,&wsaData)) != 0) {
fprintf(stderr,"WSAStartup failed with error %d\n",retval);
WSACleanup();
return -1;
}
if (port == 0){
Usage(argv[0]);
} //
// Attempt to detect if we should call gethostbyname() or
// gethostbyaddr() if (isalpha(server_name[0])) { /* server address is a name */
hp = gethostbyname(server_name);
}
else { /* Convert nnn.nnn address to a usable one */
addr = inet_addr(server_name);
hp = gethostbyaddr((char *)&addr,4,AF_INET);
}
if (hp == NULL ) {
fprintf(stderr,"Client: Cannot resolve address [%s]: Error %d\n",
server_name,WSAGetLastError());
WSACleanup();
exit(1);
} //
// Copy the resolved information into the sockaddr_in structure
//
memset(&server,0,sizeof(server));
memcpy(&(server.sin_addr),hp->h_addr,hp->h_length);
server.sin_family = hp->h_addrtype;
server.sin_port = htons(port); conn_socket = socket(AF_INET,socket_type,0); /* Open a socket */
if (conn_socket <0 ) {
fprintf(stderr,"Client: Error Opening socket: Error %d\n",
WSAGetLastError());
WSACleanup();
return -1;
} //
// Notice that nothing in this code is specific to whether we
// are using UDP or TCP.
// We achieve this by using a simple trick.
// When connect() is called on a datagram socket, it does not
// actually establish the connection as a stream (TCP) socket
// would. Instead, TCP/IP establishes the remote half of the
// ( LocalIPAddress, LocalPort, RemoteIP, RemotePort) mapping.
// This enables us to use send() and recv() on datagram sockets,
// instead of recvfrom() and sendto()
printf("Client connecting to: %s\n",hp->h_name);
if (connect(conn_socket,(struct sockaddr*)&server,sizeof(server))
== SOCKET_ERROR) {
fprintf(stderr,"connect() failed: %d\n",WSAGetLastError());
WSACleanup();
return -1;
} // cook up a string to send
//
loopcount =0;
while(1) {
wsprintf(Buffer,"This is a small test message [number %d]",loopcount++);
retval = send(conn_socket,Buffer,sizeof(Buffer),0);
if (retval == SOCKET_ERROR) {
fprintf(stderr,"send() failed: error %d\n",WSAGetLastError());
WSACleanup();
return -1;
}
printf("Sent Data [%s]\n",Buffer);
retval = recv(conn_socket,Buffer,sizeof (Buffer),0 );
if (retval == SOCKET_ERROR) {
fprintf(stderr,"recv() failed: error %d\n",WSAGetLastError());
closesocket(conn_socket);
WSACleanup();
return -1;
}
//
// We are not likely to see this with UDP, since there is no
// 'connection' established.
//
if (retval == 0) {
printf("Server closed connection\n");
closesocket(conn_socket);
WSACleanup();
return -1;
}
printf("Received %d bytes, data [%s] from server\n",retval,Buffer);
if (!loopflag){
printf("Terminating connection\n");
break;
}
else {
if ( (loopcount >= maxloop) && (maxloop >0) )
break;
}
}
closesocket(conn_socket);
WSACleanup();
}
Platform SDK Release: February 2001 Contact Platform SDK Order a Platform SDK CD Online
struct hostent* H;
char szip[]="192.168.0.1";
unsigned long ip=inet_addr(szip);
H=gethostbyaddr((char*)&ip,sizeof(ip),AF_INET);
printf("host name: %s\n",H->h_name);
129 -> 0x81
42 -> 0x2A
17 -> 0x11
99 -> 0x63
在内存里面， "81 2A 11 63"就是长整数0x63112a81，把0x63112a81传给gethostbyaddr就可以了#include <winsock.h>
int main(int argc, char* argv[])
{
WSADATA wsaData;
WSAStartup(MAKEWORD (1,1),&wsaData);
struct hostent* hostinfo;
char szip[]="129.42.17.99";
unsigned long ip=inet_addr(szip);
hostinfo = gethostbyaddr((char*)&ip,sizeof(ip),AF_INET);
printf("host name: %s\n",hostinfo->h_name); WSACleanup(); return 0;
}