在C中成功发送和接收文件大小

Question

我希望能够将文件从客户端发送到服务器。我正在使用 TCP。我正在尝试使用 fseek 等来获取文件的大小，因为我希望能够处理大文件，然后将这些字节的数据以及文件内容发送到服务器。到目前为止，根据我的 printf 消息，一切都通过并创建了文件。但是，在服务器上创建的文件是空的。我通过参数或其他方式发送和接收它的方式显然有问题，但我无法弄清楚。谁能告诉我哪里出了问题以及如何解决它，因为我很接近！

服务器部分：

if(getFile){
         
                char *tmp = buf + 9;
                char filename2[MAX_BLOCK_SIZE];
                int length, x;
                long file_size = 0;
                FILE *fp;
                strcpy(filename2, tmp);
                printf("Server receiving file name...\n");
                //first 'read' receives the file name
                fp = fopen(filename2, "wb");
                if(fp == NULL){
                    printf("File could not be opened.\n");
                    exit(1);
                }
                printf("Server receiving file...\n");
                while((x = read(sd, buf, sizeof(buf)) > 0)){ //second read now retrieving the file
                    printf("Server creating new file...\n");
                    fwrite(buf, 1, file_size, fp);
                }
            fclose(fp);
            printf("The server has received the requested document.\n");
         }

客户端：

 else if(putCommand){
            
            char *tmp = buf + 4;
            char filename[MAX_BLOCK_SIZE];
    
        long file_size;
            strcpy(filename, "filename ");
            strcat(filename, tmp);
            FILE *fp;
            printf("File name: %s\n", tmp);
            fp = fopen(tmp, "rb");
            if(fp == NULL){
                
                printf("ERROR: Requested file does not exist.\n");
                
            }
            else{
            printf("Client sending filename...\n");
            if ((nw = write(sd, filename, sizeof(filename)) < nr)){     //sending the file name to the client first
                printf("Error sending client's filename.\n");
            }
            
            //size_t file_size;
            printf("Client sending file...\n");
            fseek(fp, 0, SEEK_END);
            long filesize = ftell(fp);
            fseek(fp, 0, SEEK_SET);
            
            while((file_size = fread(buf, 1, MAX_BLOCK_SIZE, fp)) > 0){ //sending the file
            
                if ((x = write(sd, buf, filesize) < 0)){
                    printf("Error sending client file.\n");
                }
            
            }
            fclose(fp);
            
            
            }

Answer 1

这几乎是一个错字。在接收方，您有：

long file_size = 0;
...
    while(...)
        ...
        fwrite(buf, 1, file_size, fp);

所以你一直写 0 字节。

标准方式是：

    while((x = read(sd, buf, sizeof(buf)) > 0)){ //second read now retrieving the file
        printf("Server creating new file...\n");
        fwrite(buf, 1, x, fp);     // write the number of bytes returned by previous read
    }

最后一句话，我希望buf是一个真正的数组而不是一个指针...