Question

此程序正在提供分段错误。有谁能解释为什么？我尝试使用gdb。它说，错误在readFile（）上。我在使用memcpy做错了吗？我试图从客户端到服务器传输一个字节的文件。

Client.c

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


#define BUFFERSIZE 1000
#define IPSIZE 20
#define FILESIZE 100


void readFile(char *name, int sock_fd)
{
    FILE *fp = fopen(name, "rb");
    char *read_buffer, *buffer[BUFFERSIZE];
    unsigned long file_len;
    int total_size = 0, flag, rem_size;

    //Open file

    if (!fp)
    {
        fprintf(stderr, "Unable to open fp %s", name);
        return;
    }

    //Get file length
    fseek(fp, 0, SEEK_END);
    file_len=ftell(fp);
    fseek(fp, 0, SEEK_SET);

    //Allocate memory
    read_buffer = (char *)malloc(BUFFERSIZE - 23);
    if (!buffer)
    {
        fprintf(stderr, "Memory error!");
                fclose(fp);
        return;
    }

    //Read file contents into buffer

    total_size = sizeof(name) + file_len;
    printf("Total Size: %d",total_size);
    if(file_len < 976)
    {

        fread(read_buffer, sizeof(read_buffer), 1, fp);
        memcpy(buffer, &total_size, sizeof(total_size));
        memcpy(buffer[sizeof(total_size)], &name, sizeof(name));
        memcpy(buffer[sizeof(total_size)+sizeof(name)], read_buffer, sizeof(read_buffer));
        flag = write(sock_fd, htonl(buffer), strlen(buffer));   
        if (flag < 0) 
            error("ERROR writing to socket");
    }
    else
    {
        while(1)
        {
            fread(read_buffer, sizeof(read_buffer), 1, fp);
            memcpy(buffer, &total_size, sizeof(total_size));
            memcpy(buffer[sizeof(total_size)], &name, sizeof(name));
            memcpy(buffer[sizeof(total_size)+sizeof(name)], read_buffer, sizeof(read_buffer));
            flag = write(sock_fd, htonl(buffer), strlen(buffer));
            if (flag < 0) 
                error("ERROR writing to socket");
            rem_size = total_size - 1000;
            if(rem_size<0)
                break;
        }
    }           

    fclose(fp);


}


int main(int argc, char **argv)
{
    struct sockaddr_in server_addr;
    int sockfd, remote_port_no, n;
    char remote_ip[IPSIZE], file_name[FILESIZE];

    if(argc!=4)
    {
        fprintf(stderr,"Usage: ftpc <remote-IP> <remote-port> <local-file-to-transfer>");
        exit(0);
    }


    memset(&(remote_ip), '\0', sizeof(remote_ip)+1);
    memcpy(remote_ip, argv[1],sizeof(argv[1])+1);
    remote_port_no = atoi(argv[2]);
    memset(&(file_name), '\0', sizeof(file_name)+1);
    memcpy(file_name, argv[3], sizeof(argv[3])+1);

    puts(remote_ip);
    puts(file_name);
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    printf("OK");
    if(sockfd<0)
        printf("Socket creation ERROR");
    else
        printf("Socket creation success");

    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(remote_port_no);
    server_addr.sin_addr.s_addr = inet_addr(remote_ip);
    memset(&(server_addr.sin_zero), 0, sizeof(server_addr.sin_zero));

    if(connect(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
        printf("Connect ERROR");
    else
        printf("Connect Success");
    readFile(file_name, sockfd);
    return 0;
}

Server.c

#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>

#define BUFFERSIZE 1000
#define IPSIZE 20
#define FILESIZE 100

int main(int argc, char **argv)
{
int listen_fd, connect_fd, n, local_port_no, cli_len;
char buffer[BUFFERSIZE];
struct sockaddr_in serv_addr, client_addr;
FILE *fp;

if(argc != 2)
{
    fprintf(stderr,"Usage: ftps <local-port>");
    exit(0);
}

local_port_no = atoi(argv[1]);

listen_fd = socket(AF_INET, SOCK_STREAM, 0);

serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(local_port_no);
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
bzero(&(serv_addr.sin_zero), sizeof(serv_addr.sin_zero));

bind(listen_fd, (struct sockaddr *) &serv_addr, sizeof(serv_addr));

listen(listen_fd, 1);

cli_len = sizeof(client_addr);

connect_fd = accept(listen_fd, (struct sockaddr *) &client_addr, &cli_len);

recv(connect_fd, buffer, sizeof(buffer), 0);

fp = open("temp","wb");
printf("%d",sizeof(buffer));
fwrite(buffer, sizeof(buffer[0]), sizeof(buffer)/sizeof(buffer[0]), fp);
close(connect_fd);

}

更新

（gdb）列表     55 memcpy（buffer [sizeof（total_size）]，＆amp; name，sizeof（name））;     （gdb）列表     50 if（file_len＆lt; 976）     51 {     52个
    53 fread（read_buffer，sizeof（read_buffer），1，fp）;     54 memcpy（buffer，＆amp; total_size，sizeof（total_size））;     55 memcpy（buffer [sizeof（total_size）]，＆amp; name，sizeof（name））;     56 memcpy（buffer [sizeof（total_size）+ sizeof（name）]，read_buffer，sizeof（read_buffer））;     57 flag = write（sock_fd，htonl（buffer），strlen（buffer））;
    58 if（flag＆lt; 0）     59错误（“ERROR写入套接字”）;

Answer 1

buffer是一个指针数组。那是你的意图吗？

猜不是

因此它会超支

Answer 2

一些明显的问题：

您使用sizeof(read_buffer)，其中read_buffer是指向malloc缓冲区的指针。这将为您提供指针的大小，而不是缓冲区的大小。
当缓冲区包含一堆二进制数据而不是以NULL结尾的字符串时，使用strlen(buffer)。这不起作用。

c中的分段故障套接字

2 个答案: