使用从 recv() tcpServer c 接收的缓冲区的分段错误

Question

我正在尝试在 c 中创建应用程序 client/server，但是在 recv() 之后，当我尝试使用接收到的缓冲区时，程序出现分段错误（已创建核心转储），我无法工作出来。这是我在服务器端的代码：

int req_socket_id;
int comunication_socket_id;
struct sockaddr_in server_add;
struct sockaddr_in client_add;
socklen_t client_add_size;
char buffer[255];
//char mess[1024];
int i, n;
//int index;
unsigned int num;


// AF_INET = famiglia di indirizzi iPv4
req_socket_id = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

if(req_socket_id<0)
{
    printf("Socket initialization failed !!");
    return -1;
}
e
memset(&server_add, 0, sizeof(server_add)); // azzeramento struttura
server_add.sin_family = AF_INET; // dominio indirizzi IP
server_add.sin_addr.s_addr = 0; // indirizzo IP
server_add.sin_port = htons(23165); // numero di porta UDP

if(bind(req_socket_id, (struct sockaddr*) &server_add, sizeof(server_add)) < 0)
{
    perror("\nErrore associazione porta e socket!\n");
    close(req_socket_id);
    return -1;
}

if(listen(req_socket_id, 1)<0)
{
    perror("\nErrore nell'ascolto!\n");
    close(req_socket_id);
    return -1;
}

while(1)
{
    client_add_size = sizeof(client_add);
    comunication_socket_id = accept(req_socket_id, (struct sockaddr*) &client_add, &client_add_size);
    if(comunication_socket_id>=0)
    {
        //index = 0;
        char tmp[100];
        while(1)
        {
            printf("\nOk");
            //n = recv(comunication_socket_id, (char*) buffer, sizeof(buffer)+1, 0);
            //n = recv(comunication_socket_id, (void*) buffer, sizeof(buffer)+1, 0);
            n = recv(comunication_socket_id, buffer, sizeof(buffer)+1, 0);
            printf("\nReceved! n: %d", n);
            printf("\nReceved: %s", buffer);

            if(strcmp(buffer, "end")==0)
            {
                close(comunication_socket_id);
                printf("\n...socket closed");
                return -1;
            }

[...]

这是客户端代码：

unsigned long start, now;
 unsigned int *num = (unsigned int*)buffer;
 int i, n;

 TCPclient_send(buffer, strlen(buffer)+1);
 printf("\nSent: |%s|\n", buffer);
 start = clock(); // tempo iniziale attesa
 now = clock(); // tempo attuale
 while ((now - start) < TIMEOUT)
    {
        if ((n = TCPclient_receive(&buffer[i], sizeof(buffer)-i)) > 0)
         {
            i += n;
            if (i >= sizeof(unsigned int))
                {
                 // risposta completa
                 printf("Receved number %u.\r\n", ntohl(*num));
                 TCPclient_disconnect();
                 return 0;
                }
            }
        now = clock(); 
    }
 printf("No answer receved!\r\n");
 TCPclient_disconnect();

控制台服务器端输出：

davide@davide-VirtualBox:~/Documenti/RubricaTCP$ ./TCPserver 
Ok
Receved! n: 11
Errore di segmentazione (core dump creato) //-->segmentation fault, end of process

控制台客户端输出：

Insert the command (end to close): SET=A;A;A;
Sent: |SET=A;A;A;|
No answer receved!

PS：这是我第一个使用套接字的应用程序，所以我可能犯了一些愚蠢的错误。我在许多主题中寻找答案，但没有找到任何可以解决的问题。非常感谢

Answer 1

n = recv(comunication_socket_id, buffer, sizeof(buffer)+1, 0);

sizeof(buffer)+1 本质上是不正确的。应该是sizeof(buffer)。您正在使用不存在的内存。

printf("\nReceved! n: %d", n);

好的。

printf("\nReceved: %s", buffer);

错了。这应该是

printf("\nReceved: %.*s", n, buffer);

然后：

if(strcmp(buffer, "end")==0)

这也是错误的。无法保证您收到了以空字符结尾的字符串或的完整命令。这是一个字节流协议。如果你想要消息，你必须自己实现它们。编写没有读取或接收循环的网络代码或任何 I/O 代码很少是正确的。

使用从 recv() tcpServer c 接收的缓冲区的分段错误

Segmentation fault using the buffer recived from recv() tcpServer c

c

sockets

recv