c - 使用 RPC 的文件传输(任何类型的文件)

Question

我想构建一个 RPC 程序来传输任何类型的文件。但是我在运行客户端后出现段错误:例如

./file_client localhost
>get /home/ab/1.txt
>put /home/1.txt
Segmentation Fault

为了您的方便，我粘贴了我的客户端和服务器以及 .x 代码:

file.x

const MAXLEN = 1024;

/*
 * Type for storing path
 */
typedef string filename<MAXLEN>;

/*
 * Structure for sending request. Expects the path of the file
 * and the byte number at which to start reading the file from
 */
struct request {
    filename name;
    int start;
};

/*
 * Type that represents the structute for request
 */
typedef struct request request;

/*
 * Type for storing a chunk of the file that is being
 * sent from the server to the client in the current
 * remote procedure call
 */
typedef opaque filechunk[MAXLEN];

/*
 * Response sent by the server to the client as a response
 * to remote procedure call, containing the filechunk for
 * the current call and number of bytes actually read
 */
struct chunkreceive {
    filechunk data;
    int bytes;
};

/*
 * Type that represents the structure for file's chunks
 * to be received from the server
 */
typedef struct chunkreceive chunkreceive;

/*
 * File data sent by the server from client to store
 * it on the server along with the filename and the
 * number of bytes in the data
 */
struct chunksend {
    filename name;
    filechunk data;
    int bytes;
};

/*
 * Type that represents the structure for file's chunks
 * to be sent to the server 
 */
typedef struct chunksend chunksend;

/*
 * union for returning from remote procedure call, returns
 * the proper chunkdata response if everything worked fine
 * or will return the error number if an error occured
 */
union readfile_res switch (int errno) {
    case 0:
        chunkreceive chunk;
    default:
        void;
};

/*
 * Remote procedure defined in the Interface Definition Language
 * of SUN RPC, contains PROGRAM and VERSION name definitions and
 * the remote procedure signature
 */
program FTPPROG {
    version FTPVER {
        readfile_res retrieve_file(request *) = 1;
        int send_file(chunksend *) = 2;
    } = 1;
} = 0x20000011;

我的服务器代码是:

#include <rpc/rpc.h>
#include <stdio.h>
#include "file.h"

extern __thread int errno;

readfile_res* retrieve_file_1_svc(request *req, struct svc_req *rqstp)
{
    FILE *file;
    char data[1024];
    int bytes;
    static readfile_res res;

    file = fopen(req->name, "rb");
    if (file == NULL) {
        res.errno = errno;
        return (&res);
    }

    fseek (file, req->start, SEEK_SET);
    bytes = fread(res.readfile_res_u.chunk.data, 1, 1024, file);

    //res.readfile_res_u.chunk.data = data;
    res.readfile_res_u.chunk.bytes = bytes;

    /*
     * Return the result
     */
    res.errno = 0;
    fclose(file);
    return (&res);
}

int* send_file_1_svc(chunksend *rec, struct svc_req *rqstp)
{
    FILE *file;
    int write_bytes;
    static int result;

    file = fopen(rec->name, "a");
    if (file == NULL) {
        result = errno;
        return &result;
    }

    write_bytes = fwrite(rec->data, 1, rec->bytes, file);
    fclose(file);

    result = 0;
    return &result;
}

我的客户端代码是:

#include <rpc/rpc.h>
#include <stdio.h>
#include <string.h>
#include "file.h"

extern __thread int errno;

int get_file(char *host, char *name)
{
    CLIENT *clnt;
    int total_bytes = 0, write_bytes;
    readfile_res *result;
    request req;
    FILE *file;

    req.name = name;
    req.start = 0;

    /*
     * Create client handle used for calling FTPPROG on
     * the server designated on the command line. Use
     * the tcp protocol when contacting the server.
     */
    clnt = clnt_create(host, FTPPROG, FTPVER, "tcp");
    if (clnt == NULL) {
        /*
         * Couldn't establish connection with server.
         * Print error message and stop.
         */
         clnt_pcreateerror(host);
         exit(1);
    }

    file = fopen(name, "wb");

    /*
     * Call the remote procedure readdir on the server
     */
    while (1) {
        req.start = total_bytes;
        result = retrieve_file_1(&req, clnt);
        if (result == NULL) {
            /*
             * An RPC error occurred while calling the server.
             * Print error message and stop.
             */
            clnt_perror(clnt, host);
            exit(1);
        }

        /*
         * Okay, we successfully called the remote procedure.
         */
        if (result->errno != 0) {
            /*
             * A remote system error occurred.
             * Print error message and stop.
             */
            errno = result->errno;
            perror(name);
            exit(1);
        }

        /*
         * Successfully got a chunk of the file.
         * Write into our local file.
         */
        write_bytes = fwrite(result->readfile_res_u.chunk.data, 1, result->readfile_res_u.chunk.bytes, file);
        total_bytes += result->readfile_res_u.chunk.bytes;
        if (result->readfile_res_u.chunk.bytes < MAXLEN) 
            break;
    }

    fclose(file);

    return 0;
}

int put_file(char *host, char *name)
{
    CLIENT *clnt;
    char data[1024];
    int total_bytes = 0, read_bytes;
    int *result;
    chunksend chunk;
    FILE *file;

    /*
     * Create client handle used for calling FTPPROG on
     * the server designated on the command line. Use
     * the tcp protocol when contacting the server.
     */
    clnt = clnt_create(host, FTPPROG, FTPVER, "tcp");
    if (clnt == NULL) {
        /*
         * Couldn't establish connection with server.
         * Print error message and stop.
         */
         clnt_pcreateerror(host);
         exit(1);
    }

    file = fopen(name, "r");

    chunk.name = name;

    /*
     * Call the remote procedure readdir on the server
     */
    while (1) {
        read_bytes = fread(data, 1, MAXLEN, file);
        total_bytes += read_bytes;

        read_bytes = fread(chunk.data, 1, MAXLEN, file);
        chunk.bytes = read_bytes;
        result = send_file_1(&chunk, clnt);

        if (result == NULL) {
            /*
             * An RPC error occurred while calling the server.
             * Print error message and stop.
             */
            clnt_perror(clnt, host);
            exit(1);
        }

        /*
         * Okay, we successfully called the remote procedure.
         */
        if (*result != 0) {
            /*
             * A remote system error occurred.
             * Print error message and stop.
             */
            errno = *result;
            perror(name);
            exit(1);
        }

        /*
         * Successfully got a chunk of the file.
         * Write into our local file.
         */
        if (read_bytes < MAXLEN) 
            break;
    }

    fclose(file);

    return 0;
}

int read_command(char *host)
{
    char command[MAXLEN], filepath[MAXLEN];

    printf("> ");
    fflush(stdin);
    scanf("%s %s", command, filepath);

    if (strcmp(command, "get") == 0) {
        return get_file(host, filepath);
    } else if(strcmp(command, "put") == 0){
        return put_file(host, filepath);
    } else if(strcmp(command, "exit") == 0){
        exit(0);
    } else {
        return -1;
    }
}

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

   if (argc != 2) {
        fprintf(stderr, "usage: %s host\n", argv[0]);
        exit(1);
   }

   while(TRUE) {
       result = read_command(argv[1]);
   }

   return 0;
}

任何人都可以建议我在这里需要进行哪些修改。

提前致谢。

Answer 1

您已将 filechunk 类型定义为数组。您不能在 C 中将一个数组分配给另一个数组。而是将数据复制到数组中。

也就是线

   chunk.data = data;

应该是

  memcpy(chunk.data, data, read_bytes);

但在您的情况下，您可以直接读取该数组，

   read_bytes = fread(chunk.data, 1, MAXLEN, file);

然后删除chunk.data = data;代码