c - 通过 UDP c 发送结构

Question

我在通过 UDP 发送结构时遇到问题。我是网络和 C 的新手，但需要将数据作为结构(未序列化)发送。当我尝试发送时遇到段错误。新手如有错误请多多包涵。任何帮助将不胜感激。

服务器端:

struct TextMessage
{
   unsigned int SenderId;                       /* unique client identifier */
   char message[100];                           /* text message */
};

int main(int argc, char *argv[])
{
  int sock;                        /* Socket */
  struct sockaddr_in echoServAddr; /* Local address */
  struct sockaddr_in echoClntAddr; /* Client address */
  unsigned int cliAddrLen;         /* Length of incoming message */
  unsigned short echoServPort;     /* Server port */
  int recvMsgSize;                 /* Size of received message */ 

  struct TextMessage * temp = malloc(sizeof(struct TextMessage));


echoServPort = atoi(argv[1]);  /* First arg:  local port *

  /* Create socket for sending/receiving datagrams */  
  if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
      DieWithError("socket() failed");

  /* Construct local address structure */
  memset(&echoServAddr, 0, sizeof(echoServAddr));   /* Zero out structure */
  echoServAddr.sin_family = AF_INET;                /* Internet address family */
  echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */
  echoServAddr.sin_port = htons(echoServPort);      /* Local port */

  /* Bind to the local address */ 
  if (bind(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0)
      DieWithError("bind() failed");

  for (;;) /* Run forever */
  {
      /* Set the size of the in-out parameter */
      cliAddrLen = sizeof(echoClntAddr);

      /* Block until receive message from  a client */
      if ((recvMsgSize = recvfrom(sock, &temp, sizeof(temp), 0,
          (struct sockaddr *) &echoClntAddr, &cliAddrLen)) < 0)
          DieWithError("recvfrom() failed");

          printf("Handling client %s\n", inet_ntoa(echoClntAddr.sin_addr));
          printf("Incoming Length: %s\n", cliAddrLen);
      printf("Received: %s\n", temp.message);    /* Print the string in sent struct */

  }
  /* NOT REACHED */
} 

客户端:

struct TextMessage
{
    unsigned int SenderId;                       /* unique client identifier */
    char message[100];                           /* text message */
};

int main(int argc, char *argv[]) 
{ 
    int sock;                        /* Socket descriptor */
    struct sockaddr_in echoServAddr; /* Echo server address */
    struct sockaddr_in fromAddr;     /* Source address of echo */
    unsigned short echoServPort;     /* Echo server port */
    unsigned int fromSize;           /* In-out of address size for recvfrom() */
    char *servIP;                    /* IP address of server */
    int structLen;                   /* Length of string to echo */
    int respStringLen;               /* Length of received response */


    struct TextMessage newMess;

    memset(&newMess, 0, sizeof(newMess));    /* Zero out structure */
    newMess.request_Type = Send;
    newMess.SenderId = 300;
    newMess.RecipientId = 200;
    strcpy(newMess.message, argv[3]);

    printf("Size struct: %d\n", structLen);

    servIP = argv[1];           /* First arg: server IP address (dotted quad) */
    echoServPort = argv[2];  /* Use given port, if any */

/* Create a datagram/UDP socket */
    if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
    DieWithError("socket() failed");

    /* Construct the server address structure */
    memset(&echoServAddr, 0, sizeof(echoServAddr));    /* Zero out structure */
    echoServAddr.sin_family = AF_INET;                 /* Internet addr family */
    echoServAddr.sin_addr.s_addr = inet_addr(servIP);  /* Server IP address */
    echoServAddr.sin_port   = htons(echoServPort);     /* Server port */


   /* Send the string to the server */
   if (sendto(sock, (void *)&newMess, sizeof(newMess), 0, (struct sockaddr *)
           &echoServAddr, sizeof(echoServAddr)) != structLen)
       DieWithError("sendto() sent a different number of bytes than expected\n");

  close(sock);
  exit(0);
}

Answer 1

我获取了您的代码并对其进行了更新，以便它能够按您的预期工作。

代码如下:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <strings.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>

void DieWithError(char *err) {
   perror(err);
   exit(1);
}

    struct TextMessage
{
     char request_Type[100];
     unsigned int SenderId;                       /* unique client identifier */
     unsigned int RecipientId;                       /* unique client identifier */
     char message[100];                           /* text message */ 
};

int main(int argc, char *argv[])
{
     int sock;                        /* Socket */
     struct sockaddr_in echoServAddr; /* Local address */
     struct sockaddr_in echoClntAddr; /* Client address */
     unsigned int cliAddrLen;         /* Length of incoming message */
     unsigned short echoServPort;     /* Server port */
     int recvMsgSize;                 /* Size of received message */ 

  struct TextMessage * temp = malloc(sizeof(struct TextMessage));

  if (!argv[1]) {
      fprintf(stderr,"no port number provided");
     exit(1);
  }

      echoServPort = atoi(argv[1]);  /* First arg:  local port */

    /* Create socket for sending/receiving datagrams */  
  if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
    DieWithError("socket() failed");

  /* Construct local address structure */
  memset(&echoServAddr, 0, sizeof(echoServAddr));   /* Zero out structure */
  echoServAddr.sin_family = AF_INET;                /* Internet address family */
  echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */
  echoServAddr.sin_port = htons(echoServPort);      /* Local port */

  /* Bind to the local address */ 
  if (bind(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0)
     DieWithError("bind() failed");

  for (;;) /* Run forever */
  {
        /* Set the size of the in-out parameter */
        cliAddrLen = sizeof(echoClntAddr);

        /* Block until receive message from  a client */
        if ((recvMsgSize = recvfrom(sock, temp, sizeof(*temp), 0,
           (struct sockaddr *) &echoClntAddr, &cliAddrLen)) < 0)
           DieWithError("recvfrom() failed");

        printf("Handling client %s\n", inet_ntoa(echoClntAddr.sin_addr));
        printf("Incoming Length: %u\n", cliAddrLen);
        printf("Received: %s\n", temp->message);   /* Print the string in sent struct */

   }
      /* NOT REACHED */

        close(sock);
        return 0;
  } 

对于客户端:

  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <string.h>
  #include <strings.h>
  #include <arpa/inet.h>
  #include <netinet/in.h>
  #include <sys/types.h>
  #include <sys/socket.h>

  void DieWithError(char *err) {
       perror(err);
       exit(1);
  }

  struct TextMessage
  {
       char request_Type[100];
       unsigned int SenderId;                       /* unique client identifier */
       unsigned int RecipientId;                       /* unique client identifier */
       char message[100];                           /* text message */
  };

  int main(int argc, char *argv[]) 
  { 
       int sock;                        /* Socket descriptor */
       struct sockaddr_in echoServAddr; /* Echo server address */
       struct sockaddr_in fromAddr;     /* Source address of echo */
       unsigned short echoServPort;     /* Echo server port */
       unsigned int fromSize;           /* In-out of address size for recvfrom() */
       char *servIP;                    /* IP address of server */
       int structLen;                   /* Length of string to echo */
       int respStringLen;               /* Length of received response */


       if (!argv[1]) {
              fprintf(stderr,"No server IP sepcified at arg 1\n");
              exit(1);
       }

       else if (!argv[2]) {
              fprintf(stderr,"No port Number Sepcified at arg 2\n");
              exit(2);
       }

       else if (!argv[3]) {
              fprintf(stderr,"no message string specified at arg 3\n");
              exit(3);
       }



        struct TextMessage newMess = { "Send" , 300 , 200 };

        //    memset(&newMess, 0, sizeof(newMess));    /* Zero out structure */
        //    strcpy(newMess.request_Type,"Send"); 
        //    newMess.SenderId = 300;
        //    newMess.RecipientId = 200;
        strncpy(newMess.message, argv[3],sizeof(argv[3]));

        printf("Size struct: %d\n", sizeof(newMess));

        servIP = argv[1];           /* First arg: server IP address (dotted quad) */
        echoServPort = atoi(argv[2]);  /* Use given port, if any */

        /* Create a datagram/UDP socket */
        if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
               DieWithError("socket() failed");

        /* Construct the server address structure */
        memset(&echoServAddr, 0, sizeof(echoServAddr));    /* Zero out structure */
        echoServAddr.sin_family = AF_INET;                 /* Internet addr family */
        echoServAddr.sin_addr.s_addr = inet_addr(servIP);  /* Server IP address */
        echoServAddr.sin_port   = htons(echoServPort);     /* Server port */

        int tempint = 0;

        /* Send the string to the server */
        tempint = sendto(sock, (struct TextMessage*)&newMess, (1024+sizeof(newMess)), 0, (struct sockaddr *)
         &echoServAddr, sizeof(echoServAddr)); 

        if (tempint == -1 ) {

               printf("Sent struct size: %d\n", tempint);
               DieWithError("sendto() sent a different number of bytes than expected\n");
        }

        close(sock);
        exit(0);
}