分段错误 - 通过服务器向客户端发送对象

Question

我正在尝试在 linux 中创建客户端服务器应用程序。服务器向客户端发送对象，但客户端写入分段错误。这是代码。 Snake 是二维数组的类。

客户端发送消息“p”，服务器正在创建对象，将发送给客户端。

服务器端：

  int main(int argc, char *argv[])
  {

int sockfd, newsockfd;
socklen_t cli_len;
struct sockaddr_in serv_addr, cli_addr;
int n;
char buffer[256];


if (argc < 2) 
{
    fprintf(stderr,"usage %s port\n", argv[0]);
    return 1;
}

bzero((char*)&serv_addr, sizeof(serv_addr)); 
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(atoi(argv[1]));

sockfd = socket(AF_INET, SOCK_STREAM, 0); 
if (sockfd < 0)
{
    perror("Error creating socket");
    return 1;
}

if (bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) 
{
     perror("Error binding socket address");
     return 2;
}
while(sockfd){
listen(sockfd, 5); 
cli_len = sizeof(cli_addr);

newsockfd = accept(sockfd, (struct sockaddr*)&cli_addr, &cli_len); 

if (newsockfd < 0)
{
    perror("ERROR on accept");
    return 3;
}

bzero(buffer,256);
n = read(newsockfd, buffer, 255); 
if (n < 0)
{
    perror("Error reading from socket");
    return 4;
}


// if client send 'p'
if(*buffer == 'p'   ){ 
        Snake *snake = new Snake(); 

    send(newsockfd,reinterpret_cast<const char*>(&snake), sizeof(snake),0);
  }
}



//printf("Here is the message: %s\n", buffer); 

const char* msg = "I got your message";
n = write(newsockfd, msg, strlen(msg)+1);
if (n < 0)
{
    perror("Error writing to socket");
    return 5;
}

close(newsockfd);

close(sockfd);

}

客户端：

 int main(int argc, char *argv[])
 {
int sockfd = 0,newsockfd, n;
struct sockaddr_in serv_addr;
struct hostent* server;
socklen_t cli_len, serv_len;

char buffer[999999];
struct sockaddr_in cli_addr;

if (argc < 3) 
{
    fprintf(stderr,"usage %s hostname port\n", argv[0]);
    return 1;
}

server = gethostbyname(argv[1]); 
if (server == NULL)
{
    fprintf(stderr, "Error, no such host\n");
    return 2;
}

bzero((char*)&serv_addr, sizeof(serv_addr)); 
serv_addr.sin_family = AF_INET;
bcopy(
    (char*)server->h_addr,
    (char*)&serv_addr.sin_addr.s_addr,
    server->h_length
);
serv_addr.sin_port = htons(atoi(argv[2]));
//while(sockfd >= 0){
sockfd = socket(AF_INET, SOCK_STREAM, 0); 
if (sockfd < 0)
{
    perror("Error creating socket");
    return 3;
}

if(connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0)  
{
     perror("Error connecting to socket");
     return 4;
}   

printf("Please enter a message: "); 
bzero(buffer,256);
fgets(buffer, 255, stdin); 

n = write(sockfd, buffer, strlen(buffer));  

if (n < 0)
{
     perror("Error writing to socket");
     return 5;
}

 Snake *snake ;

recv(sockfd,reinterpret_cast<char*>(&snake), sizeof(snake),0);

if (n < 0)
{
     perror("Error reading from socket");
     return 6;
}

printf("%s\n",buffer);

close(sockfd);
close(newsockfd);
return 0;
 }  

感谢您的回答。

Answer 1

在客户端

 Snake *snake ;

recv(sockfd,reinterpret_cast<char*>(&snake), sizeof(snake),0);

尝试读入 Snake，但您还没有创建任何内容。所以未初始化的指针会给你分段错误。

另外，sizeof(snake) 是指针的大小（如 4 个字节），而不是指向的对象的大小。这发生在服务器和客户端中。