C语言 编译 .c 代码时未声明 socklen_t

socklen_t undeclared when compiling .c code

提问by jarkam

I am trying to compile this .c code in windows using MinGW (gcc file.c -o compiled.exe):

我正在尝试使用 MinGW (gcc file.c -ocompiled.exe) 在 windows 中编译这个 .c 代码：

/***************************************************/ 
/* AUTHOR         :  LAW CHIU YUEN                 */
/* FILENAME     :  smtpr.c                         */
/***************************************************/ 

#ifdef WIN32
#include <windows.h>
#include <winsock.h>
#else
#define closesocket close
#include <unistd.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <arpa/inet.h>
#include <ctype.h>


//#define MYPORT 40711    // the port users will be connecting to
#define PORT 25
#define MAXBUFLEN 1024      // max buffer size
#define RELAY_NAME 255 // max length of file name
#define BACKLOG 10     // how many pending connections queue will hold
#define MAXDATASIZE 512 // max number of bytes we can get at once 
#define SQMAXDATASIZE 1048576 //1024 * 1024
#define RECVTIME 100    // max number of time to wait for client's message
#define MAXEMAILADDRESS 320 // 64 + 1 + 255 
#define MAXRCPT 50     //max number of mail receipients
/* State1 */
#define ACCEPT 0
#define HELO 1
#define MAILFROM 2
#define RCPTTO 3
#define DATA 4
#define MESSAGE 5
#define QUIT 6
#define RELAY 7
/* State2 */
#define FIRSTHELO 0
#define SECONDHELO 1
#define MAXHELO 1024

/*  tokenize mailto string, each time return the first email address */
/* eg.  [email protected],[email protected],[email protected] -->  [email protected]  */
char* tokenize(char *mailto){
     const char delimiters[] = ",";
     char *token, *cp;
     printf("b4 strtok: mailto:%s\n",mailto);     
                /* Make writable copy.  */
     token = strtok (mailto, delimiters);      /* token => "words" */
     printf("tokenize() speaking : mailto: %s\n",mailto);
     printf("tokenize() speaking : token: %s\n",token);
     return token;

}

/*  tokenize mailto string, each time return the email address other then the first one*/
/* first call:  [email protected],[email protected],[email protected] -->  [email protected]  */
/* second call:  [email protected],[email protected],[email protected] -->  [email protected]  */
char* tokenize_null(){
     const char delimiters[] = ",";
     char *token, *cp;

     token = strtok (NULL, delimiters);      /* token => "words" */
     printf("tokenize_null() speaking : token: %s\n",token);
     return token;
}

/* take in an email_address, and header; */
/*  convert to :  header: email_address  */
char* compose_mailheader(char *header,char *mail){
  char *a = malloc(strlen(mail)+30);
  char *b = NULL;
  char *c = NULL;
  strcpy(a, header);

  b = strcat(a, mail);
  c = strcat(b, "\r\n");
  printf("compose_mailheader:   b=%s\n", b);
  return b;
}

/*  1. receive message from smtp server  */
void receive(int fd, char* command, char *buf){
 int numbytes;

   if ((numbytes=recv(fd, buf, MAXDATASIZE, 0)) == -1) {
        fprintf(stderr,"error in receiving\n");
        exit(1);
    }
    buf[numbytes] = '
C:\MinGW\bin>gcc file.c -o compiled.exe
file.c: In function `main':
file.c:973: error: `socklen_t' undeclared (first use in this function)
file.c:973: error: (Each undeclared identifier is reported only once
file.c:973: error: for each function it appears in.)
file.c:973: error: syntax error before "addr_len"
';
    printf("    receive() Received buf : %s",buf);
    if ( strstr(buf, command) != NULL ){
    printf("    receive() Received command : %s\n",command);
    }else{
    }
}
/*  helo  */
/*  1. called by relaymail()  */
/*  2. interact with a smtp server */
void helo(int sockfd){
  int numbytes;
  char buf2[MAXDATASIZE];
  char buf[MAXDATASIZE];
  printf("\n");
  printf("helo is called\n");
  /*receive 220*/
  receive(sockfd, "220 ", buf);

  /* send helo */
  if (send(sockfd, "HELO server\r\n", 13, 0) == -1)
    perror("HELO SERVER");
//  printf("sent HELO SERVER\n");

/* receive 250*/
  receive(sockfd, "250 ", buf);

/*      testing    */  
//  if (send(sockfd, "HELO server\r\n", 13, 0) == -1)
//    perror("HELO SERVER");

//  receive(sockfd, "250 ", buf);
}

/*  mailfrom  */
/*  1. called by relaymail()  */
/*  2. interact with a smtp server */
void mailfrom(int sockfd,char *mail_from){
  char buf[MAXDATASIZE] = "MAIL FROM:";

  char *out;
  int numbytes;
  int i;
  printf("\n");
  printf("mailfrom is called\n");

  /*  compose the "MAIL FROM:[email protected]" message  */ 
  strcat(buf, mail_from);
  strcat(buf, "\r\n");
  printf("mailfrom() speaking: buf=%s\n", buf);
  printf("mailfrom() speaking: strlen(buf)=%i\n", strlen(buf));

  /* send out */
  if( send(sockfd, buf, strlen(buf), 0) == -1 )
     perror("mailfrom()");

  /* receive 250*/
  receive(sockfd, "250 ", buf);

}  //mailfrom

/*  1. called by rcptto()  */
/*  2. interact with a smtp server */
void rcptto2(int sockfd,char *mailtos){
  char buf[MAXDATASIZE]="";
  char *a;
  char *out;
  int numbytes;
  int i,len;
  printf("\n");
  printf("rcptto2 is called\n");
  /*  compose the "RCPT TO:[email protected]" message  */ 
    strcat(buf, "RCPT TO:");
    strcat(buf, tokenize_null());
    strcat(buf, "\r\n");
    printf("rcptto2() speaking: buf=%s\n", buf);
    printf("rcptto2() speaking: strlen(buf)=%i\n", strlen(buf));

    /*  send out */
    if( send(sockfd, buf, strlen(buf), 0) == -1 )
       perror("rcptto()");

    /*  receive 250*/
    receive(sockfd, "250 ", buf);
    /*  clear the buffer  */
    for(i=0; i<strlen(buf);i++){
     buf[i]='
$ find /usr/include -name \*.h -print0 |xargs -0 grep -w socklen_t
...
/usr/include/unistd.h:typedef __socklen_t socklen_t;
...
/usr/include/sys/socket.h:         socklen_t *__restrict __addr_len);
';
    }//for()

}

/*  rcptto  */
/*  1. called by relaymail()  */
/*  2. interact with a smtp server */
void rcptto(int sockfd,char *mailtos, int mailto_num){
  char buf[MAXDATASIZE] = "RCPT TO:";
  char *a;
  char *out;
  int numbytes;
  int i,len;
  printf("\n");
  printf("rcptto is called\n");

/* sending the first address... */
    /*  compose the "RCPT TO:[email protected]" message  */ 
    strcat(buf, tokenize(mailtos));
    strcat(buf, "\r\n");
    printf("rcptto() speaking: buf=%s\n", buf);
    printf("rcptto() speaking: strlen(buf)=%i\n", strlen(buf));

    /*  send out */
    if( send(sockfd, buf, strlen(buf), 0) == -1 )
       perror("rcptto()");

    /*  receive 250*/
    receive(sockfd, "250 ", buf);
    /*  clear the buffer  */

    /*  handle multiple recipients case*/
    for(i=0;i<mailto_num-1;i++)
      rcptto2(sockfd, mailtos);


/* sending remaining addresses... */
}  //rcptto

/*  1. called by relaymail()  */
/*  2. interact with a smtp server */
void data(int sockfd){
  char buf[MAXDATASIZE] = "";
  printf("\n");
  printf("data() is called\n");

  /*  send "DATA"  */
  if( send(sockfd, "DATA\r\n", 6, 0) == -1 )
     perror("data()");

  /*  receive 354  */
  receive(sockfd, "354 ", buf);
}


/*  1. called by relaymail()  */
/*  2. interact with a smtp server */
void message(int sockfd, char *msg){
  int times,i,j;
  int remainder;
  printf("\n");
  char out[1025];
  printf("message() is called\n");

  times = strlen(msg) / MAXDATASIZE;
  remainder = strlen(msg) - (times * MAXDATASIZE);

  printf("remainder: %i\n", remainder);
  printf("times: %i\n", times);

  for (i=0;i< times;i++){
     for (j=0;j< 1024;j++)
        out[j]= msg[1024*i + j];
     out[1024 +1] = '
#include <ws2tcpip.h>
';

     printf("sending msg: %i\n", i);
      if( send(sockfd, out, 1025, 0) == -1 );
  }
  printf("end while: %i\n", i);
  printf("out: %s\n", out);
     for (j=0;j< remainder;j++)
        out[j]= msg[1024*times + j];
        out[remainder +1] = '
typedef int socklen_t;
';
  if( send(sockfd, out, remainder+1, 0) == -1 )
       perror("message");
       printf("out: %s\n", out);
}

/*  1. called by relaymail()  */
/*  2. interact with a smtp server */
void quit(int sockfd){
  char buf[MAXDATASIZE] = "";
  printf("\n");
  printf("quit() is called\n");

  /*  send "QUIT"  */
  if( send(sockfd, "QUIT\r\n", 6, 0) == -1 )
     perror("quit()");

  /*  receive 354  */
  receive(sockfd, "250 ", buf);
}


/*relay mail to a email server*/
void relaymail(char *relay,char *mail_from, char *mailto, int mailto_num, char *msg){

    int sockfd, numbytes;  
    char buf[MAXDATASIZE];
    struct hostent *he;
    struct sockaddr_in their_addr; // connector's address information 
    int state = 1;
    int logswitch = 0; 
  int logwhile = 0;


    if ((he=gethostbyname(relay)) == NULL) {  // get the host info 
        fprintf(stderr,"gethostbyname fail\n");
        exit(1);
    }

    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        fprintf(stderr,"fail to create socket\n");
        exit(1);
    }

    their_addr.sin_family = AF_INET;    // host byte order 
    their_addr.sin_port = htons(PORT);  // short, network byte order 
    their_addr.sin_addr = *((struct in_addr *)he->h_addr);
    memset(&(their_addr.sin_zero), '
#include <stdint.h>
typedef uint32_t socklen_t;
', 8);  // zero the rest of the struct 

    if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1) {
        fprintf(stderr,"connect fail\n");
        exit(1);
    }

   while (state <7 && logwhile <10){  /*  make sure the program won't run indefinitely  */

   logwhile++;
   /*   log   */ 
//      printf("\n");
//   printf("logwhile = %i\n", logwhile);
//   printf("state = %i\n", state);
//      printf("\n");

   switch (state){
    case HELO :
     helo(sockfd);
     state++;
     printf ("end of case HELO\n");
     break;
    case MAILFROM :
     mailfrom(sockfd, mail_from);
     state++;
     printf ("relaymail():  end of case MAILFROM\n");    
     break;
    case RCPTTO :
     rcptto(sockfd, mailto, mailto_num);
     state++;
     printf ("relaymail():  end of case RCPTTO\n");         
     break;    
    case DATA :
     data(sockfd);
     state++;
     printf ("relaymail():  end of case DATA\n");
     break;
    case MESSAGE :
     message(sockfd, msg);
     printf ("relaymail():  end of case MESSAGE\n");
     state++;
     printf ("relaymail():  end of case MESSAGE\n");
    case QUIT :
     quit(sockfd);
     state++;
     printf ("end of case QUIT\n");
     closesocket(sockfd);
     break;

    default :
     break;    
    }
  }  // while()
    closesocket(sockfd);
}


/*  remove  < >   */
char* remove_brackets(char* input)
{
  int length;
  int i, j;
  char* output;

  length = strlen(input);
  output = (char*) malloc(length + 1); 
  j = 0;

  /* copy character of input which in not equal to < or > to output */
  for (i=0; i<length; i++)
    if ((input[i]!='<') && (input[i]!='>'))
    {
      output[j] = input[i];
      j++; 
    }     
  output[j] = '
#include <ws2tcpip.h>
';

  return output;
}


/* trim the space(s) before and after the string */
char* trim_space(char* input)
{
  int i, j, length, is_ch, is_end, end_pos;
  char *output;

  /* trim the space(s) before the string */
  length = strlen(input);
  output = (char*) malloc (length+1);
  is_ch = 0;
  is_end = 0;
  j = 0;

  for(i=0; i<length; i++)
  {
    /* copy input characters to output */
    if (is_ch==1 || !isspace(input[i]))
    {
      output[j] = input[i];
      j++;
      is_ch = 1;
    }
 }
  output[j] = '
#include <winsock2.h>
#include <Ws2ipdef.h>   
';

  /* trim the space(s) after the string */
  length = strlen(output);
  end_pos = length-1;
  is_end = 0;

  for (i=0; i<length; i++)
    if (is_end==0 && isspace(output[i]))
    {
      is_end = 1;
      end_pos = i;   
    }   
    else if (!isspace(output[i]))
      is_end = 0; 

  output[end_pos] = '##代码##';

  return output;
}


/* convert :    MAIL FROM: [email protected]  --->  [email protected] */
char *extractemail(const char *buf, const int i){
char * email = NULL;
char * tmp_email = NULL;
char * tmp_email2 = NULL;
char * tmp_email3 = NULL;

 /*           extract email address              */
/*  1. remove MAIL FROM:  */
    email = malloc(strlen(buf));
        strcpy(email,buf);
        email += i;
        printf("\n");
        printf("email =%s\n", email);
        printf("email length =%i\n", strlen(email));
        printf("\n");
/*  2. trim head and trailing whitespace  */
        tmp_email = trim_space(email);
        printf("trimmed email= %s\n", tmp_email);
/*  3. remove <>  */
    tmp_email2 = remove_brackets(tmp_email);
    printf("remove<> email= %s\n", tmp_email2);
/*  4. trim again */
//    tmp_email3 = trim_space("[email protected]");
//    printf("\n");
//    printf("extracted email= ~~~~~~%s~~~~~~\n", tmp_email3);
//    printf("\n");

//    printf("extracted email= ~~~~~~%s~~~~~~\n", tmp_email3);
    return tmp_email2;
}


/* check if email address is a valid one  */
int check_email_validity(const char *address) {
  // check if email address is valid
 // return 1 if valid
 // return 0 if invalid

  int number = 0;
  const char *a, *host;
  static char *special_characters = "()<>@,;:\\"[]";
   /* validate name  */
  for (a = address;  *a;  a++) {
    if (*a == '\"' && (a == address || *(a - 1) == '.' || *(a - 1) == 
        '\"')) {
      while (*++a) {
        if (*a == '\"') break;
        if (*a == '\' && (*++a == ' ')) continue;
        if (*a <= ' ' || *a >= 127) return 0;
      }
      if (!*a++) return 0;
      if (*a == '@') break;
      if (*a != '.') return 0;
      continue;
    }
    if (*a == '@') break;
    if (*a <= ' ' || *a >= 127) return 0;
    if (strchr(special_characters, *a)) return 0;
  }
  if (a == address || *(a - 1) == '.') return 0;

  /* next we validate the host portion (name@host) */
  if (!*(host = ++a)) return 0;
  do {
    if (*a == '.') {
      if (a == host || *(a - 1) == '.') return 0;
      number++;
    }
    if (*a <= ' ' || *a >= 127) return 0;
    if (strchr(special_characters, *a)) return 0;
  } while (*++a);

  return (number >= 1);
}

int main(int argc, char *argv[])
{
 int sockfd, new_fd;  // listen on sock_fd, new connection on new_fd
    struct sockaddr_in my_addr;    // my address information
    struct sockaddr_in their_addr; // connector's address information
    int sin_size;
    int yes=1;
    socklen_t addr_len;
    int numbytes=0;
    char buf[MAXBUFLEN] = "";
    char tmp_msg[MAXBUFLEN] ="";
    char message[SQMAXDATASIZE];
    char message_buf[10000];
    char *msg = message;
    char quit[MAXBUFLEN];
    int MYPORT;
    char relay[RELAY_NAME];
    int i,j;
    char *email = NULL;
    char *email2 = NULL;
    char *mail_from = NULL;
    char *mail_to = NULL;
    char *tmp_mail = NULL;
    char mailtos[2000];
    int mailto_num =0;
    char *data = NULL;
    char *data2 = NULL;
    char *quit1 = NULL;
    char *quit2 = NULL;



    int state1 = 0;  //  
    int state2 = 0;  //  keep track of number of 'helo's
        int logwhile = 0;
    char hardcode_email[15] = "[email protected]";


    #ifdef WIN32
      WSADATA wsaData;
      WSAStartup(0x0101, &wsaData);
    #endif

    /* check number of parameters */
    if ( argc != 3 && argc !=2 ) {
  fprintf(stderr,"usage: smtpr <port number> (<relay server>)\n");
  exit(1);
    }

    /* fill in port number */
    MYPORT = atoi(argv[1]);
    if ( MYPORT <= 0){
 fprintf(stderr, "Invalid port number.\nusage: smtpr <port number> (<relay server>)\n");
        exit(1);
    }

    /* fill in the server relay to */
    if (argc == 2) strcpy(relay, "some.mail.server");
    else if (argc == 3) strcpy(relay, argv[2]);
    printf("relay to %s\n", relay);


/*create a TCP socket */
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }

    printf("port number : %i\n", MYPORT);

    my_addr.sin_family = AF_INET;         // host byte order
    my_addr.sin_port = htons(MYPORT);     // short, network byte order
    my_addr.sin_addr.s_addr = htonl(INADDR_ANY); // automatically fill with my IP
    memset(&(my_addr.sin_zero), '##代码##', 8); // zero the rest of the struct

/* bind to the port number*/
    if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {
        perror("bind");
        exit(1);
    }
/* listen*/
    if (listen(sockfd, BACKLOG) == -1) {
        perror("listen");
        exit(1);
    }  


    /* slow the receiving speed */
//    sleep(1);

while(1){

logwhile++;


switch ( state1 ){

case ACCEPT:
/* accept */
        sin_size = sizeof(struct sockaddr_in);
        if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size)) == -1) {
            perror("accept");
        }
        printf("server: got connection from %s\n",inet_ntoa(their_addr.sin_addr));

/* send msg : 220 */       
       if (send(new_fd, "220 cylaw's smtpr ready\r\n", 25, 0) == -1)
            perror("send");


/*proceed to next state*/
        printf("state1 = %i\n", state1);
        state1++;
    break;

case HELO:

      if(state2 == 0){ //state2 keep track of if this is the first HELO
          if ((numbytes=recv(new_fd, buf, MAXDATASIZE, 0)) == -1) {
              perror("recv");
              exit(1);
          }
        }
          buf[numbytes] = '##代码##';

/*   log   */ 
    printf("case HELO\n");
    printf("============\n");
        printf("buf :%s\n", buf);

/* check on length */
        if ( strlen(buf) < 6 || strlen(buf) > MAXDATASIZE ){
             printf("550 Syntax: <HELO>\n");
         if (send(new_fd, "550 Syntax: <HELO|EHLO> <hostname>\r\n", 36, 0) == -1)
         perror("HELO send");
         }

/* compare (case-insensitively) the first 4 bytes of buf with "HELO" and "EHLO"  */

        if ( (strncasecmp(buf, "HELO ", 5) != 0) && (strncasecmp(buf, "EHLO ", 5) != 0 )  ){
             printf("550 Syntax: <HELO>\n");
         if (send(new_fd, "550 Syntax: <HELO|EHLO> <hostname>\r\n", 36, 0) == -1)
         perror("HELO-1 send");
         }

/* not implement case : helo<space>aaaaa<space> */
        if ( buf[5] == '##代码##' && buf[5] == ' ' ){
             printf("550 Syntax: <HELO|EHLO> <hostname>\n");
         if (send(new_fd, "550 Syntax: <HELO|EHLO> <hostname>\r\n", 36, 0) == -1)
         perror("HELO-2 send");
         }

/* send 250 OK */
    printf("250 HELO OK\n");
        if ( send( new_fd, "250 HELO OK\r\n", 13, 0 ) == -1 )
        perror("HELO-250-OK send");
        printf("\n");



/*proceed to next state*/
        state1++;
        state2++;
        break; //case HELO

case MAILFROM :

        if ((numbytes=recv(new_fd, buf, MAXDATASIZE, 0)) == -1) {
            perror("recv");
            exit(1);
        }
        buf[numbytes] = '##代码##';


/*   log   */ 
        printf("\n");
    printf("case MAILFROM\n");
    printf("=============\n");
        printf("buf :%s\n", buf);



/* HELO */
    if ( (strncasecmp(buf, "HELO ", 5) == 0) || (strncasecmp(buf, "EHLO ", 5) == 0 )  ){
    printf("HELO received at case MAILFROM, go back to case HELO\n");
     state1--;
     break;
    }

/*  check "MAIL FROM:"   */
        if ( strncasecmp(buf, "MAIL FROM:", 10) != 0 ){
             printf("550 Syntax: MAIL FROM: <email-address>\n");
         if (send(new_fd, "550 Syntax: MAIL FROM: <email-address>\r\n", 40, 0) == -1)
           perror("MAIL FROM: send()");
          exit(1);
        }

/*  extract email address  */
    mail_from = extractemail(buf, 10);


/*  check email validity  */  

        if ( check_email_validity(mail_from) == 0 ){  //0 - invalid 1 - valid
             printf("550 Invalid email address\r\n");
         if (send(new_fd, "550 Invalid email address\r\n", 27, 0) == -1)
          perror("Email address send()");
         break; //case MAILFROM

         }

/* send 250 OK */
    printf("250 MAIL FROM OK\n");
        if ( send( new_fd, "250 MAIL FROM OK\r\n", 18, 0 ) == -1 )
        perror("MAILFROM-250-OK send()");

        printf("\n");

        state1++;
        break; //case MAILFROM

case RCPTTO :

/*  check if this is the first MAIL FROM: <> line  */
if ( mailto_num == 0){  
        if ((numbytes=recv(new_fd, buf, MAXDATASIZE, 0)) == -1) {
            perror("recv");
            exit(1);
        }
        buf[numbytes] = '##代码##';
}


/*   log   */ 
        printf("\n");
    printf("case RCPTTO\n");
    printf("=============\n");
        printf("state1 = %i\n", state1);
        printf("buf :%s\n", buf);


/*  check RCPT TO: <...>   */
        if ( strncasecmp(buf, "RCPT TO:", 8) != 0 ){
             printf("550 Syntax: RCPT TO: <email-address>\n");
             if (send(new_fd, "550 Syntax: RCPT TO: <email-address>\r\n", 38, 0) == -1)
         perror("MAIL FROM: send()");
        }

/*  extract email address  */
   mail_to = extractemail(buf, 8);  // 8 = strlen("RPCT TO:")


/*  recipients address on to mailtos []*/
  strcat(mailtos, mail_to);
  strcat(mailtos, ",");
  mailto_num++;
  printf("mailtos %s\n", mailtos);
  printf("mailto_num %i\n", mailto_num);



/*  check email validity  */  

        if ( check_email_validity(mail_to) == 0 ){
             printf("550 Invalid email address\n");
         if (send(new_fd, "550 Invalid email address\r\n", 27, 0) == -1)
         perror("RCPTTO address send()");
         break; //case MAILFROM

         }

/* send 250 OK */
    printf("250 RCPT TO OK\n");
        if ( send( new_fd, "250 RCPT TO OK\r\n", 16, 0 ) == -1 )
        perror("MAILFROM-250-OK send()");

        state1++;
    break; // case RCPTTO

case DATA :

        if ((numbytes=recv(new_fd, buf, MAXDATASIZE, 0)) == -1) {
            perror("recv");
            exit(1);
        }
        buf[numbytes] = '##代码##';


     /*   log   */ 
        printf("\n");
    printf("case DATA\n");
    printf("=============\n");
        printf("state1 = %i\n", state1);
        printf("buf :%s\n", buf);


/*  multiple recipients */

    if ( strncasecmp(buf, "RCPT TO:", 8 ) == 0){
     printf("Multiple recipients -- Go back to state RCPT TO\n");
     printf("\n");
     state1--;
     break;
    }

        if ( strncasecmp(buf,"DATA", 4) != 0 ){  
             printf("451 Syntax: DATA\n");      
         if (send(new_fd, "451 Syntax: DATA\r\n", 18, 0) == -1)
          perror("DATA send");
         } else{



/* send 354 OK */
//    send( new_fd, "354 End\r\n", 10, 0 );
    printf("354 End data with <CR><LF>.<CR><LF>\n");
        if ( send( new_fd, "354 End data with <CR><LF>.<CR><LF>\r\n", 37, 0 ) == -1 ){
         perror("MAILFROM-354-OK send()");
         printf("354 error\n");
         exit(1);
       }

        printf("\n");
      }


  state1++;
 break; // case DATA


case MESSAGE :

       printf("\n");
    printf("case MESSAGE\n");
    printf("============\n");

    i=0;
    while(i<10000){
     i++;
         if ((numbytes=recv(new_fd, message_buf, 9999, 0)) == -1) {
             perror("recv");
             exit(1);
         }
         message_buf[numbytes] = '##代码##';
/*  log  */
//         printf("message_buf:\n\n%s", message_buf);        
/*  append message_buf to message  */         
         strcat(message, message_buf);

         if (strstr (message_buf, "\r\n.\r\n") != NULL ){
/* send 250 OK */
          printf(". found\n");
          if ( send( new_fd, "250 message received\r\n", 22, 0 ) == -1 )
             perror("MESSAGE");
          printf("message:\n\n %s\n", message);
          state1++;
      break;
         }//if()
       }//while()
       state1++;
       break;

case QUIT :

        if ((numbytes=recv(new_fd, quit, MAXDATASIZE, 0)) == -1) {
            perror("recv");
            exit(1);
        }
        quit[numbytes] = '##代码##';

     /*   log   */ 
    printf("\n");
    printf("case QUIT\n");
    printf("=============\n");
        printf("buf :%s\n", quit);
        printf("\n");

    /*  trim space "     QUIT       "  */    
//        quit1 = malloc(strlen(quit));
//        strcpy(quit1, quit);
//        printf("quit :%s\n", quit1);
//        quit2 = trim_space(quit1);
//        printf("quit :%s\n", quit1);


/*  check QUIT   */
        if ( strncasecmp(quit, "QUIT", 4) != 0 ){
             state1 =  QUIT;
         if (send(new_fd, "550 Syntax: QUIT\r\n", 18, 0) == -1)
         perror("QUIT");
        }else{

/* send 221 OK */
        if ( send( new_fd, "221 QUIT.\r\n", 11, 0 ) == -1 )
        perror("QUIT");
printf("QUIT!\n");
closesocket(new_fd);
state1++;
break;
}
 break; // case QUIT

case RELAY :
  relaymail(relay,mail_from,mailtos,mailto_num, msg);

  /* go back to ACCEPT states  */
  state1 = ACCEPT;  

/* reset variables  */
  strcpy(buf, "");
  strcpy(tmp_msg, "");
  strcpy(message, "");
    strcpy(message_buf, "");
  strcpy(quit,"");
    i=0;j=0;
    email = NULL;
    email2 = NULL;
    mail_from = NULL;
    mail_to = NULL;
    tmp_mail = NULL;
  strcpy(mailtos, "");
    mailto_num =0;
    data = NULL;
    data2 = NULL;
    quit1 = NULL;
    quit2 = NULL;
  state2 = 0;

break;

default : break;

}//switch
} // while(1)

        close(new_fd);

    #ifdef WIN32
      WSACleanup();
    #endif

    return 0;
}

But its failing with the error:

但它因错误而失败：

##代码##

I tried googling the error but all i found is info about compiling specific softwares but not what could cause it.

我尝试使用谷歌搜索错误，但我发现的只是关于编译特定软件的信息，而不是可能导致它的原因。

What can I do to fix this error?

我能做些什么来修复这个错误？

采纳答案by Paul Tomblin

Figure out which .h file it is defined in, and include it. On a Unix/Linux box, I'd start with a find/grep in /usr/include

找出它是在哪个 .h 文件中定义的，并将其包含在内。在 Unix/Linux 机器上，我会从 /usr/include 中的 find/grep 开始

##代码##

Looks like it's defined in unistd.h - but you've already got that one included, so I guess you're covered on that side. I don't know how you'd find which file to include on the Windows side.

看起来它是在 unistd.h 中定义的 - 但你已经包含了那个，所以我想你已经被覆盖了。我不知道您如何找到要在 Windows 端包含的文件。

回答by mickael

Under mingw you can try to include ws2tcpip.h

在 mingw 下你可以尝试包含 ws2tcpip.h

##代码##

回答by paxdiablo

Check your socket.h- that's most likely where it's defined. Your code compiles fine with CygWin since the socket.hcontains (by virtue of the fact it includes cygwin/socket.h):

检查您的socket.h- 这很可能是它定义的地方。您的代码可以用 CygWin 编译得很好，因为socket.h包含（由于它包含的事实cygwin/socket.h）：

##代码##

As a kludge, you could try adding that line to your own code. But you should still investigate whyit's missing and maybe raise a bug report.

顺便说一句，您可以尝试将该行添加到您自己的代码中。但是您仍然应该调查它为什么丢失并可能提出错误报告。

There's a great many pages complaining that MinGW doesn't support socklen_t, for example here, here, hereand here, the last of which states that it lives in ws2tcpip.has I defined it in my kludge above.

有很多页面抱怨 MinGW 不支持 socklen_t，例如这里、这里、这里和这里，最后一个声明它存在于ws2tcpip.h我在上面的 kludge 中定义的那样。

回答by André Wagner

According to the Unix Specification, socket.h makes available a type, socklen_t, which is an unsigned opaque integral type of length of at least 32 bits. Apparently MingW doesn't include it.

根据Unix 规范，socket.h 提供了一种类型 socklen_t，它是一种长度至少为 32 位的无符号不透明整数类型。显然 MingW 不包括它。

You can define it as:

您可以将其定义为：

##代码##

回答by ATLdev

For Windows, to get a definition for socklen_t:

对于 Windows，要获取 socklen_t 的定义：

##代码##

Valid as of VS2017 and this writing; based on https://docs.microsoft.com/en-us/windows/win32/api/ws2tcpip/nf-ws2tcpip-getnameinfo.

自 VS2017 和本文起生效；基于https://docs.microsoft.com/en-us/windows/win32/api/ws2tcpip/nf-ws2tcpip-getnameinfo。

Two other headers I've found I needed to port a particular Linux based socket source file to Windows are:

我发现需要将特定的基于 Linux 的套接字源文件移植到 Windows 的另外两个标头是：

##代码##