memcpy tcp 소켓의 세그먼트 오류

Question

서버에 연결중인 클라이언트를 쓰고 있습니다. 나는 TCP 소켓의 memcpy() 라인 124에 Segmentation Fault를 가지고있다. UDP 연결을 사용하여 네트워크에서 서버의 IP 주소를 얻고 싶으면 IP를 얻은 다음 TCP 연결을 통해 연결하려고합니다. TCP 연결 자체의 코드는 새로운 파일에서 컴파일 할 수 있기 때문에 작동합니다. 나는 문제가 어디 있는지 이해하지 못한다.

#include <stdio.h>  
#include <sys/types.h> 
#include <ifaddrs.h> 
#include <netinet/in.h> 
#include <string.h> 
#include <arpa/inet.h> 
#include <string.h> 
#include <memory.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <sys/types.h> 
#include <netdb.h> 
#include "main.h" 

int developer=1; 
struct myHelloMsg { 
    char myIp[25]; 
    char myID[25]; 
}; 
int FindMyIp(char myIpAddr[], char myMask[], char myBroad[]); 
int RecvBroadTime(int sockfd, struct sockaddr_in server_addr); 
void CheckID(char myUserID[]); 

int main() { 
    char myIpAddr[25], myMask[25], myBroad[25], myUserID[25]=""; 
    char otherUserIp[25], otherUserID[25]; 
    struct myHelloMsg myMsg, rxMsg; 
    CheckID(myUserID); 
    int checkConnection; 
    disconnected: ; 
    checkConnection=0; 
    if (developer==1) printf("\nSearching for a network..\n"); 
    while (checkConnection == 0) { 
     checkConnection = FindMyIp(myIpAddr, myMask, myBroad); 
     if (checkConnection==0) { 
      if (developer==1) printf("--Disconnected..\n"); 
      sleep(5); 
     } 
    } 
    if (developer==1) printf("\n--Connected..\nIP Address\t: %s\n", myIpAddr); 
    if (developer==1) printf("Subnet Mask\t: %s\n", myMask); 
    if (developer==1) printf("Broadcast IP\t: %s\n", myBroad); 

    int i=0; 
    for (i=0;i<25;i++) { 
     myMsg.myIp[i]=myIpAddr[i]; 
     myMsg.myID[i]=myUserID[i]; 
    } 
    struct hostent *hptr = gethostbyname(myBroad); 
    if (hptr == NULL) { 
     if (developer==1) printf("Error while transmitting broadcast message..\n"); 
     return 0; 
    } 
    // create socket for initial UDP communication 
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0); 
    struct sockaddr_in server_addr; 
    bzero(&server_addr, sizeof(struct in_addr)); 
    server_addr.sin_family = AF_INET; 
    server_addr.sin_port = htons(5051); 
    server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); 
    memcpy(&server_addr.sin_addr, hptr->h_addr_list[0], sizeof(struct in_addr)); 
    int opt = 1; 
    setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &opt, sizeof(int)); 
    int error=0; 
    if (developer==1) printf("--Contacting other users in the network..\n"); 
    sendto(sockfd, &myMsg, sizeof(myMsg), 0, (struct sockaddr *) &server_addr, sizeof(struct sockaddr_in)); 
    int foundSomeone=0; 
    //try to connect with others for 5 times - because of UDP unreliable connection 
    int countTries=0, received=0, lastTry=0; 
    while (countTries<5) { 
     foundSomeone = RecvBroadTime(sockfd, server_addr); 
     if (foundSomeone == 1) { 
      if (developer==1) printf("An answer has been received..\n"); 
      socklen_t ssize = sizeof(struct sockaddr_in); 
      recvfrom(sockfd, &rxMsg, sizeof(rxMsg), 0, (struct sockaddr *) &server_addr, &ssize); 
      received=1; 
      countTries=5; 
     } 
     else if (foundSomeone == 0) { 
      if (developer==1) printf("Timeout(%d try)..\n", countTries+1); 
      sendto(sockfd, &myMsg, sizeof(myMsg), 0, (struct sockaddr *) &server_addr, sizeof(struct sockaddr_in)); 
      if (countTries==4) { 
       lastTry=1; 
      } 
     } 
     else { 
      if (developer==1) printf("--Error..\n"); 
     } 
     countTries++; 
    } 
    if ((lastTry==1)&&(countTries==5)) { 
     foundSomeone = RecvBroadTime(sockfd, server_addr); 
     if (foundSomeone == 1) { 
      if (developer==1) printf("An answer has been received..\n"); 
      socklen_t ssize = sizeof(struct sockaddr_in); 
      recvfrom(sockfd, &rxMsg, sizeof(rxMsg), 0, (struct sockaddr *) &server_addr, &ssize); 
      received=1; 
     } 
     else if (foundSomeone == 0) { 
      if (developer==1) printf("--No one is connected to the current network..\n"); 
     } 
     else { 
      if (developer==1) printf("There has been an error while trying to contact other users..\n"); 
     } 
    } 
    close(sockfd); 
    // someone else is connected to the network 
    // i am gonna behave as a client in during the synchronization step 
    if (received==1) { 
     if (developer==1) printf("Contact made with user %s (%s).\n", myMsg.myID, myMsg.myIp); 
     // check if the user belong to friends i am sharing content with 
     i=0; 
     for (i=0;i<25;i++) { 
      otherUserIp[i]=rxMsg.myIp[i]; 
      otherUserID[i]=rxMsg.myID[i]; 
     } 
     int socktcp = socket(AF_INET, SOCK_STREAM, 0); 
     struct hostent *hptr_tcp = gethostbyname(otherUserIp); 
     struct sockaddr_in server_addr_tcp; 
     bzero(&server_addr_tcp, sizeof(struct sockaddr_in)); 
     server_addr_tcp.sin_family = AF_INET; 
     server_addr_tcp.sin_port = htons(5054); 
     printf("a\n"); 
     memcpy(&server_addr_tcp.sin_addr, hptr_tcp->h_addr_list[0], sizeof(struct in_addr)); 
     printf("a\n"); 
     if (connect(socktcp, (struct sockaddr *) &server_addr_tcp, sizeof(struct sockaddr_in))<0) { 
      printf("-Error..\n"); 
     } else { 
      printf("Connection with %s established.. Ready for synchronization step..\n", otherUserID); 
     } 
    } 

    return 0; 
} 


int RecvBroadTime(int sockfd, struct sockaddr_in server_addr) { 
    fd_set socks; 
    struct timeval t; 
    t.tv_sec = 1; 
    t.tv_usec = 0; 
    FD_ZERO(&socks); 
    FD_SET(sockfd, &socks); 
    return select(sockfd+1, &socks, NULL, NULL, &t); 
} 

int FindMyIp(char myIpAddr[], char myMask[], char myBroad[]) { 
    struct ifaddrs * ifAddrStruct=NULL; 
    struct ifaddrs * ifa=NULL; 
    void * tmpAddrPtr=NULL; 
    getifaddrs(&ifAddrStruct); 
    int i=0, connected=0; 
    ifa = ifAddrStruct; 
    while (i!=1) { 
     if (((ifa ->ifa_addr->sa_family==AF_INET)&&(ifa->ifa_name[0]=='e')&&(ifa->ifa_name[1]=='n')&&(ifa->ifa_name[2]=='1'))||((ifa ->ifa_addr->sa_family==AF_INET)&&(ifa->ifa_name[0]=='e')&&(ifa->ifa_name[1]=='t')&&(ifa->ifa_name[2]=='h')&&(ifa->ifa_name[3]=='0'))) { 
      i=1; 
      connected=1; 
     } else { 
      if (ifa->ifa_next == NULL) return connected; 
      ifa = ifa->ifa_next; 
     } 
    } 
    tmpAddrPtr=&((struct sockaddr_in *)ifa->ifa_addr)->sin_addr; 
    inet_ntop(AF_INET, tmpAddrPtr, myIpAddr, INET_ADDRSTRLEN); 
    tmpAddrPtr=&((struct sockaddr_in *)ifa->ifa_netmask)->sin_addr; 
    inet_ntop(AF_INET, tmpAddrPtr, myMask, INET_ADDRSTRLEN); 
    tmpAddrPtr=&((struct sockaddr_in *)ifa->ifa_broadaddr)->sin_addr; 
    inet_ntop(AF_INET, tmpAddrPtr, myBroad, INET_ADDRSTRLEN); 
    return connected; 
} 

void CheckID(char myUserID[]) { 
    FILE *fp; 
    if((fp=fopen("userData.txt", "r+"))==NULL) { 
     printf("Error while opening the file..\n"); 
    } 
    else { 
     fscanf(fp, "%25s", myUserID); 
     if (strlen(myUserID)==0) { 
      printf("First time you open this app..\nInsert your User ID: "); 
      scanf("%s", myUserID); 
      fprintf(fp, "%-25s", myUserID); 
     } 
     else { 
      printf("Welcome back %s..\n", myUserID); 
     } 
     fclose(fp); 
    } 
} 

Answer 1

나는 gethostbyname()을 사용하여 브로드 캐스트 주소를 확인할 수 없다고 말하고 싶습니다. 또한

---

: gethostbyname()가 사용되지 않습니다, 대신 getnameinfo()를 사용합니다.