#include <errno.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <stdlib.h> #include <string.h> #include <netinet/in.h> #include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h>  typedef struct _NSS_HEADER {   unsigned short     ProtocolVersion;    /* 協議版本信息 */   unsigned short     MsgType;        /* 消息類型 */   unsigned short     TransactionNo;     /* 傳輸編號 */   unsigned short     PacketLength;      /* 數據包長度,包括Header */ }NSS_HEADER;   int str_echo(int sockfd, unsigned short no) {   ssize_t readLen;   ssize_t writeLen;   char  buf[8];    NSS_HEADER *hdr = (NSS_HEADER*)buf;   memset( hdr, 0, sizeof(NSS_HEADER) );   hdr->TransactionNo = no;    // 寫數據   int nWriteLen = 0;   while ( true )   {     writeLen = write(sockfd, &buf[nWriteLen], sizeof(NSS_HEADER)-nWriteLen); //    printf( "write %d/n", writeLen);         if (writeLen < 0 && errno == EINTR)     {       continue;     }     else if ( writeLen < 0 )     {       perror ( "write:" );       return -1;     }      nWriteLen += writeLen;     // 已寫完，直接返回     if (nWriteLen >= sizeof(NSS_HEADER) )     {       break;     }   }    printf( "send data successed. trans no: %d/n", no );    // 讀數據   int nReadLen = 8;   while ( true )   {         readLen = read(sockfd, buf, nReadLen); //    printf( "read: %d/n", readLen );     if (readLen < 0 && errno == EINTR)     {       continue;     }     else if ( readLen <= 0 )     {       perror( "read:");       return -1;     }     else      {       nReadLen -= readLen;       if (nReadLen <= 0 )       {         break;       }     }   }    printf( "read response successed./n" );    return 0; }  int main(int argc, char **argv) {   printf("client ip: %s/n", argv[1]);   printf("client port: %s/n", argv[2]);   printf("server ip: %s/n", argv[3]);   printf("server port: %s/n", argv[4]);    printf("/n service starting.../n/n");   while( true )   {     int   socketFd;     struct sockaddr_in svrAddr;     struct sockaddr_in localAddr;      socketFd = socket (AF_INET, SOCK_STREAM, 0);     if ( -1 == socketFd )     {       perror( "socket:" );       continue;     }      // 設置地址可復用     int option = 1;     setsockopt( socketFd, SOL_SOCKET, SO_REUSEADDR, &option, sizeof(option) );     // 客戶端IP     memset(&localAddr, 0, sizeof(localAddr));     localAddr.sin_family = AF_INET;     localAddr.sin_addr.s_addr = inet_addr( argv[1]);     localAddr.sin_port = htons (atoi(argv[2]));      int bindResult = bind(socketFd, (struct sockaddr *) &localAddr, sizeof(localAddr));     if ( -1 == bindResult )     {       perror( "bind:" );       sleep(10);       close(socketFd);       continue;     }      // 服務器IP     memset(&svrAddr, 0, sizeof(svrAddr));     svrAddr.sin_family = AF_INET;     svrAddr.sin_addr.s_addr = inet_addr( argv[3]);     svrAddr.sin_port = htons (atoi(argv[4]));      // 不斷重連     int connResult = connect(socketFd, (struct sockaddr *) &svrAddr, sizeof(svrAddr));     if ( -1 == connResult )     {       perror( "connect:" );       sleep(10);       close(socketFd);       continue;     }          printf (" connect %s:%s successed./n", argv[3], argv[4] );      static unsigned short no = 0;     // 連接成功，每分鐘發送一次數據     for ( ; ; )     {       if ( -1 == str_echo(socketFd, no++) )       {         break;       }              sleep( 60 );     }     close(socketFd);   } } 

#include <errno.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <stdlib.h> #include <string.h> #include <netinet/in.h> #include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h>  struct _NSS_HEADER {   unsigned short     ProtocolVersion;    /* 協議版本信息 */   unsigned short     MsgType;        /* 消息類型 */   unsigned short     TransactionNo;     /* 傳輸編號 */   unsigned short     PacketLength;      /* 數據包長度,包括Header */ }NSS_HEADER;   void str_echo(int sockfd) {   ssize_t readLen;   ssize_t writeLen;   char  buf[8];    while ( true )   {     readLen = read(sockfd, buf, 8);     if (readLen < 0 && errno == EINTR)     {       continue;     }     else if ( readLen <= 0 )     {       perror( "read:");       return ;     }     printf( "recv data successed. data len: %d/n", readLen );      int nWriteLen = 0;     while ( true )     {       writeLen == write(sockfd, &buf[nWriteLen], readLen-nWriteLen);        if (writeLen < 0 && errno == EINTR)       {         continue;       }       else if ( writeLen < 0 )       {         perror ( "write:" );         return;       }        nWriteLen += writeLen;        // 已寫完，直接返回       if (nWriteLen >= readLen )       {         break;       }     }      printf( "send data successed. data len: %d/n", readLen );   } }  int main(int argc, char **argv) {   printf( "server ip: %s/n", argv[1] );   printf( "server port: %s/n", argv[2] );    printf( "/nservice starting ... /n/n" );    int   listenfd, connfd;   pid_t  childpid;   socklen_t clilen;   struct sockaddr_in cliaddr, servaddr;    listenfd = socket (AF_INET, SOCK_STREAM, 0);   if ( -1 == listenfd )   {     perror( "socket:" );     exit(-1);   }    // 設置地址可復用   int option = 1;   setsockopt( listenfd, SOL_SOCKET, SO_REUSEADDR, &option, sizeof(option) );    memset(&servaddr, 0, sizeof(servaddr));   servaddr.sin_family = AF_INET;   servaddr.sin_addr.s_addr = inet_addr( argv[1]);   servaddr.sin_port = htons (atoi(argv[2]));    int bindResult = bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr));   if ( -1 == bindResult )   {     perror( "bind:" );     exit(-1);   }    int listenResult = listen(listenfd, 5);   if ( -1 == listenResult )   {     perror( "listen:" );     exit(-1);   }    for ( ; ; )    {     clilen = sizeof(cliaddr);     connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &clilen);     if ( -1 == connfd )     {       perror( "accept:" );       continue;     }      printf ("accept %s successed.fd: %d/n", inet_ntoa(cliaddr.sin_addr), connfd );      if ( (childpid = fork()) == 0)      { /* child process */       close(listenfd);  /* close listening socket */        str_echo(connfd);  /* process the request */        printf ("disconnect from %d ./n", connfd );         exit (0);     }   }   close(connfd);     /* parent closes connected socket */ }