一个TCP/IP转发的列子(转)

#include
#include
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#ifndef _SCO_DS
#include
#endif
#include
#define LISTENMAX 2
int g_iCltNum=0;
extern int errno;

void WriteErrLog(const char *i_sFormat,...)
{
va_list args;
char   *sLogFile;
FILE   *fLogFile;
time_t tWriteTime;
char   sWriteTime[20];
pid_t ThisPid;

ThisPid=getpid();
time(&tWriteTime);
cftime(sWriteTime,"%Y/%m/%d %H:%M:%S",&tWriteTime);
sLogFile=getenv("ERRFILE");

if(sLogFile != NULL) fLogFile=fopen(sLogFile,"a+");

if(sLogFile != NULL && fLogFile !=NULL)
fprintf(fLogFile,"[%6d]%s : ",ThisPid,sWriteTime);
va_start(args,i_sFormat);
if(sLogFile != NULL && fLogFile !=NULL)
vfprintf(fLogFile,i_sFormat,args);
va_end(args);
if(sLogFile != NULL && fLogFile != NULL) fclose(fLogFile);
}

/* passivesock allocate & bind a server socket using tcp or ucp */
int PassiveSock(const char *service,const char *transport,int qlen)
{
struct servent *pse;
struct protoent *ppe;
struct sockaddr_in sin;
int s,type,optval,optlen;

memset(&sin,0,sizeof(sin));
sin.sin_family=AF_INET;
sin.sin_addr.s_addr=INADDR_ANY;//?(u_long)0x00000000
if (pse=getservbyname(service,transport))
sin.sin_port=htons(ntohs((u_short)pse->s_port));
else if ((sin.sin_port=htons((u_short)atoi(service)))==0)
WriteErrLog("Warning:Can't get service!!:%s\n",service);
/* map protocol name to protocol number */
if ((ppe=getprotobyname(transport))==0)
WriteErrLog("Warning:Can't get protocol number:%d!!\n",transport);

if (!strcmp(transport,"udp"))
type=SOCK_DGRAM;
else
type=SOCK_STREAM;

/* allocate a socket */
s=socket(PF_INET,type,ppe->p_proto);
if (s<0)
WriteErrLog("Can't create socket\r\n");

       optval = 1;
       optlen = sizeof(optval);
       if(setsockopt(s,SOL_SOCKET,SO_REUSEPORT,(char *)&optval,optlen) == -1)
            WriteErrLog("Warning:setsockopt error:%s\n",strerror(errno));


/* bind the socket */
if (bind(s,(struct sockaddr *)&sin,sizeof(sin))<0)
WriteErrLog("Warning:Can't bind to %s port: %s!!\n",service,strerror(errno));

if (type==SOCK_STREAM && listen(s,qlen)<0)
WriteErrLog("Warning:Can't listen on port!!:%s\n",strerror(errno));
WriteErrLog("SockRecvServer:Listening on port %s.......\n",service);
return s;
}

void catchcld(int sig)
{
int   iStat;
/*等待进程结束*/
wait(&iStat);
/*子进程结束后进程数量减一*/
g_iCltNum--;
}

/*
函数：tcp代理服务
功能：创建一个Socket服务，等待客户端连接，在客户段和服务器端建立代理连接
参数：
代理服务端口号
服务器地址
服务器端口号
允许最大连接数
*/


main(int argc,char *argv[])
{
int isSockId,iSockId,icSockId;

struct sockaddr_in sAddrIn;

unsigned char cDataBuf[1024];
#ifdef _SCO_DS
int iAddrLen;
#else
size_t iAddrLen;
#endif
pid_t iChildPid;
int iRet=0;

char cService[20];
char cHost[20];
char cPort[20];
char cNum[20];
int   iPNum;

fd_set rset;


       if(argc != 5)
       {
printf("\n金鹰UNIX通用代理服务器\n");
printf("版本：v1.0\n");
printf("南京金鹰国际软件版权所有\n\n");
            printf("Usage: %s 代理服务端口号 服务器地址 服务器端口号   允许最大连接数 \n\n",argv[0]);
            exit(0);
       }
memset(cService,0x0,sizeof(cService));
memcpy(cService,argv[1],strlen(argv[1]));
memset(cHost,0x0,sizeof(cHost));
memcpy(cHost,argv[2],strlen(argv[2]));
memset(cPort,0x0,sizeof(cPort));
memcpy(cPort,argv[3],strlen(argv[3]));
memset(cNum,0x0,sizeof(cNum));
memcpy(cNum,argv[4],strlen(argv[4]));
iPNum = atoi(cNum);

/*捕捉子进程结束的信号*/
signal(SIGCHLD,catchcld);
/*忽略管道信号*/
signal(SIGPIPE,SIG_IGN);

/*将进程设置成精灵进程 交由init管理*/
if(fork()>0)exit(0);
setsid();

/*创建被动服务套接字*/
iSockId=PassiveSock(cService,"tcp",LISTENMAX);
if (iSockId<0)
{
WriteErrLog("创建sock在服务%s失败\n",cService);
exit(-1);
}
while(1)
{
signal(SIGCHLD,catchcld);
signal(SIGPIPE,SIG_IGN);
errno=0;
iAddrLen=sizeof(sAddrIn);

/*等待客户端的连接*/
if((isSockId=accept(iSockId,(struct sockaddr *)&sAddrIn,&iAddrLen))<(long)0)
{
WriteErrLog("Accept error (%d):%s\n",errno,strerror(errno));
/*连接出错 1 秒后继续服务*/
sleep(1);continue;
}

/*WriteTest("Accepted connection(%d) From host(%s) port(%d)\n",isSockId,inet_ntoa(sAddrIn.sin_addr),ntohs(sAddrIn.sin_port));*/

/*进程数量大于iPNum时 1秒后继续服务*/
if(g_iCltNum > iPNum - 1)
{
close(isSockId);
sleep(1); continue;
}
/*创建进程*/
if((iChildPid=fork()) < 0)
{
WriteErrLog("Fork error :%s!!\n",strerror(errno));
close(isSockId);
/*出错1秒后 继续服务*/
sleep(1); continue;
}
/*父进程继续等待客户端的连接 进程数量加一*/
if(iChildPid>0) { close(isSockId);g_iCltNum++;continue; }

close(iSockId);

/*连接到服务器*/
icSockId=ConnectSock(cHost,cPort,"tcp",0);
if (icSockId<0)
            {
                     WriteErrLog("连接(%s:%s)失败(%d):%s\n",cHost,cPort,errno,strerror(errno));
close(isSockId);
exit(0);
            }
/*WriteTest(" %d to   %d\n",isSockId,icSockId);*/

while(1)
{
FD_ZERO(&rset);
FD_SET(icSockId,&rset);
FD_SET(isSockId,&rset);
iRet=select(isSockId+1,&rset,NULL,NULL,NULL);
/*如果连接在客户机的套接字可读*/
if(FD_ISSET(isSockId,&rset))
{
/*读取客户请求*/
iRet=recv(isSockId,cDataBuf,1024,0);
if(iRet == 0 )
{
close(icSockId);
close(isSockId);
exit(0);
}
/*WriteTest("U recv(%d)=%s\n",iRet,cDataBuf);*/
/*转发到服务器*/
if(send(icSockId,cDataBuf,iRet,0)<0)
{
close(icSockId);
close(isSockId);
exit(0);
}
}
/*如果连接在服务器的套接字可读*/
if(FD_ISSET(icSockId,&rset))
{
/*读服务器的应答*/
iRet=recv(icSockId,cDataBuf,1024,0);
if(iRet == 0 )
{
close(icSockId);
close(isSockId);
exit(0);
}
/*WriteTest("D recv(%d)=%s\n",iRet,cDataBuf);*/
/*转发到客户*/
if(send(isSockId,cDataBuf,iRet,0)<0)
{
close(icSockId);
close(isSockId);
exit(0);
}
}
}
}
}