局域网连接的问题
有没有办法知道局域网哪台机子是服务器。
如何判断本地是否与服务器连接。
开机后没有与服务器连接上，后来连上了应该怎样获得连接的信息。
由于编写的软件是运行在客户端的，服务器端什么都没有，只是被动的接受消息。如果用PING来判断是否连通，应该怎么写，请教达人。最好能有个例子或代码，谢谢！急用，今天就要搞定
[解决办法]
ping的代码
#define TIMEOUT 3
static int toflag;
static int sock;
static char sendbuf[1500],recvbuf[1500];
static int datalen=56;
static int nsend=0;
static pid_t pid;
static char *host,namebuf[50];
static struct sockaddr_in to;
static struct sockaddr_in from;
extern CLog g_log;
void err_quit(char *msg)
{
//perror(msg);
printf("%s\n", msg);
//exit(1);
}
unsigned short in_cksum(unsigned short *addr,int len)
{
int nleft=len;
int sum=0;
unsigned short *w=addr;
unsigned short answer=0;
while(nleft>1)
{
sum+=*w++;
nleft-=2;
}
if(nleft==1)
{
*(unsigned char *)(&answer)=*(unsigned char *)w;
sum+=answer;
}
sum=(sum>>16)+(sum&0xffff);
sum+=(sum>>16);
answer=~sum;
return(answer);
}
void pinger(void)
{
struct icmp *icp;
int cc;
int i;
bzero(sendbuf,1500);
icp=(struct icmp *)sendbuf;
icp->icmp_type=ICMP_ECHO;
icp->icmp_code=0;
icp->icmp_seq=nsend++;
icp->icmp_id=pid;
gettimeofday((struct timeval *)icp->icmp_data,NULL);
cc=datalen+8;
icp->icmp_cksum=in_cksum((unsigned short *)icp,cc);
i=sendto(sock,sendbuf,cc,0,
(struct sockaddr *)&to,sizeof(struct sockaddr));
if(i<0||i!=cc)
err_quit("sendto error");
}
int proc_pack(ssize_t len,struct timeval *tvrecv)
{
int hlen1,icmplen;
double rtt;
struct ip *ip;
struct icmp *icmp;
struct timeval *tvsend;
char buf[50];
ip=(struct ip *)recvbuf;
hlen1=ip->ip_hl<<2;
icmp=(struct icmp *)(recvbuf+hlen1);
if((icmplen=len-hlen1)<8)
{
err_quit("icmplen1");
return -1;
}
if(icmp->icmp_type==ICMP_ECHOREPLY)
{
if(icmp->icmp_id!=pid)
return -1;
if(icmplen<16)
return -1;
return 0;
}
return -1;
}
void sig_alrm(int signo)
{
signal(SIGALRM,sig_alrm);
pinger();
alarm(TIMEOUT);
//return;
}
static void _alarmproc(int sig_num)
{
signal(SIGALRM, _alarmproc);
toflag = 1;
}
int ping_loop(void)
{
int size;
int i;
int len;
ssize_t n;
fd_set rset, wset;
struct timeval tv;
int timeout = 1;
int bread;
size = 60 * 1024;
if((sock=socket(AF_INET,SOCK_RAW,IPPROTO_ICMP))<0)
{
//err_quit("create raw socket erro\n");
return -1;
}
setsockopt(sock, SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));
FD_ZERO(&rset);
FD_SET(sock, &rset);
wset = rset;
tv.tv_sec = TIMEOUT;
tv.tv_usec = 0;
if(select(sock + 1, &rset, &wset, NULL, &tv) == 0)
{
//printf("in select()...\n");
}
for(i = 0; i < 3; i++)
{
len=sizeof(from);
pinger();
if(errno==ETIMEDOUT)
{
//printf("pinger time out...\n");
g_log.printlog(93001);
return -1;
}
n=recvfrom(sock,recvbuf,1500,0,(struct sockaddr *)&from,&len);
if(n<0)
{
if(errno==EINTR)
return -1;
//continue;
else
return -1;
//err_quit("recvfrom");
}
gettimeofday(&tv,NULL);
if(proc_pack(n,&tv) == 0)
return 0;
}
return -1;
}
int gsnping(char *hostip)
{
struct sigaction act;
struct hostent *ht;
int ret;
pid=getpid();
act.sa_handler=sig_alrm;
act.sa_flags=0;
signal(SIGALRM,sig_alrm);
to.sin_family=AF_INET;
to.sin_addr.s_addr=inet_addr(hostip);
if(to.sin_addr.s_addr!=(unsigned int)-1)
host=hostip;
else
{
if(!(ht=gethostbyname(hostip)))
err_quit("gethostbyname");
to.sin_family=ht->h_addrtype;
memmove(&to.sin_addr,ht->h_addr,ht->h_length);
strncpy(namebuf,ht->h_name,sizeof(namebuf)-1);
host=namebuf;
}
ret = ping_loop();
close(sock);
return ret;
}
[解决办法]
///////////////////////////////////////////
// ping.cpp文件
#include "../common/initsock.h"
#include "../common/protoinfo.h"
#include "../common/comm.h"
#include <stdio.h>
CInitSock theSock;
typedef struct icmp_hdr
{
unsigned char icmp_type;// 消息类型
unsigned char icmp_code;// 代码
unsigned short icmp_checksum;// 校验和
// 下面是回显头
unsigned short icmp_id;// 用来惟一标识此请求的ID号，通常设置为进程ID
unsigned short icmp_sequence;// 序列号
unsigned long icmp_timestamp; // 时间戳
} ICMP_HDR, *PICMP_HDR;
int main()
{
// 目的IP地址，即要Ping的IP地址
char szDestIp[] = "10.16.115.178";// 127.0.0.1
// 创建原始套节字
SOCKET sRaw = ::socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
// 设置接收超时
SetTimeout(sRaw, 1000, TRUE);
// 设置目的地址
SOCKADDR_IN dest;
dest.sin_family = AF_INET;
dest.sin_port = htons(0);
dest.sin_addr.S_un.S_addr = inet_addr(szDestIp);
// 创建ICMP封包
char buff[sizeof(ICMP_HDR) + 32];
ICMP_HDR* pIcmp = (ICMP_HDR*)buff;
// 填写ICMP封包数据
pIcmp->icmp_type = 8;// 请求一个ICMP回显
pIcmp->icmp_code = 0;
pIcmp->icmp_id = (USHORT)::GetCurrentProcessId();
pIcmp->icmp_checksum = 0;
pIcmp->icmp_sequence = 0;
// 填充数据部分，可以为任意
memset(&buff[sizeof(ICMP_HDR)], 'E', 32);
// 开始发送和接收ICMP封包
USHORTnSeq = 0;
char recvBuf[1024];
SOCKADDR_IN from;
int nLen = sizeof(from);
while(TRUE)
{
static int nCount = 0;
int nRet;
if(nCount++ == 4)
break;
pIcmp->icmp_checksum = 0;
pIcmp->icmp_timestamp = ::GetTickCount();
pIcmp->icmp_sequence = nSeq++;
pIcmp->icmp_checksum = checksum((USHORT*)buff, sizeof(ICMP_HDR) + 32);
nRet = ::sendto(sRaw, buff, sizeof(ICMP_HDR) + 32, 0, (SOCKADDR *)&dest, sizeof(dest));
if(nRet == SOCKET_ERROR)
{
printf(" sendto() failed: %d \n", ::WSAGetLastError());
return -1;
}
nRet = ::recvfrom(sRaw, recvBuf, 1024, 0, (sockaddr*)&from, &nLen);
if(nRet == SOCKET_ERROR)
{
if(::WSAGetLastError() == WSAETIMEDOUT)
{
printf(" timed out\n");
continue;
}
printf(" recvfrom() failed: %d\n", ::WSAGetLastError());
return -1;
}
// 下面开始解析接收到的ICMP封包
int nTick = ::GetTickCount();
if(nRet < sizeof(IPHeader) + sizeof(ICMP_HDR))
{
printf(" Too few bytes from %s \n", ::inet_ntoa(from.sin_addr));
}
// 接收到的数据中包含IP头，IP头大小为20个字节，所以加20得到ICMP头
ICMP_HDR* pRecvIcmp = (ICMP_HDR*)(recvBuf + 20); // (ICMP_HDR*)(recvBuf + sizeof(IPHeader));
if(pRecvIcmp->icmp_type != 0)// 回显
{
printf(" nonecho type %d recvd \n", pRecvIcmp->icmp_type);
return -1;
}
if(pRecvIcmp->icmp_id != ::GetCurrentProcessId())
{
printf(" someone else's packet! \n");
return -1;
}
printf(" %d bytes from %s:", nRet, inet_ntoa(from.sin_addr));
printf(" icmp_seq = %d. ", pRecvIcmp->icmp_sequence);
printf(" time: %d ms", nTick - pRecvIcmp->icmp_timestamp);
printf(" \n");
::Sleep(1000);
}
return 0;
}
