C 套接字下载功能传输损坏的文件

如何解决C 套接字下载功能传输损坏的文件

我正在尝试在 C 套接字中实现下载。这个想法是在客户端获取文件的大小并一次发送 1024 个字节，多次，然后发送剩余的字节。在服务器端，您将收到这些字节，并将它们附加到运行时创建的文件中。

这是客户端代码。

char localfilename[260];
if (get_string_between_spaces(localfilename,buffer,sizeof(buffer),1,2) == -1)   {
    /*
    the function above goes through the buffer where a command is stored,like "download hi.txt hello.txt and stores into localfilename "hi.txt"
    */
    send_message(sock,"error",sizeof("error")); //this function is a wrapper for send()
    goto jump;
}
FILE *pLOCALFILE;
pLOCALFILE = fopen(localfilename,"rb");
if (!pLOCALFILE) {
    send_message(sock,"File not found on target system.Exiting..\n",sizeof("File not found on target system.Exiting..\n"));
    goto jump;
} else {
    send_message(sock,"File found target system going on...\n",sizeof("File found target system going on...\n"));
}
int size_of_file = get_file_size(pLOCALFILE); //returns the size of the file
int remainder = size_of_file % 1024; 
int quotient = size_of_file / 1024;

send_integer(sock,size_of_file);
send_integer(sock,remainder);
send_integer(sock,quotient);
for (int i = 0; i < quotient; i++) {
    /*
     you will want to send 1024 bytes for quotient times 
    */
    fread(container,1024,pLOCALFILE);
    send(sock,container,sizeof(container),0);
    memset(container,sizeof(container));
}
//send over the remaining bytes
//if quotient == 0 the for loop doesn't get executed,the file transfer being done in one send() instruction
fread(container,remainder,pLOCALFILE);
send(sock,0);
memset(container,sizeof(container));
fclose(pLOCALFILE);

这是服务器代码。

char filename[260];
get_string_between_spaces(filename,2,3);
/*
    the function above goes through the buffer 
where a command is stored,like "download hi.txt 
hello.txt and stores into localfilename "hello.txt"
*/
FILE *pFILETOWRITE;
pFILETOWRITE = fopen(filename,"ab");//open the file in append bytes mode
if (pFILETOWRITE) {
    printf("The file %s has been opened.\n",filename);
} else {
    printf("Couldn't open the %s file.\n",filename);
    goto jump;
}
            
recv(client_socket,receive_response,sizeof(receive_response),0);
printf("%s\n",receive_response);
//the receive response above receives the ok to continue if we were able to open the file on the client
char containerOFmode[1024];
bzero(containerOFmode,sizeof(containerOFmode));
int size_of_client_file = recv_integer(client_socket);
int remainder = recv_integer(client_socket);
int quotient= recv_integer(client_socket);
int bytes_transferred = 0;
printf("%d bytes are to be transferred.\n",size_of_client_file);
printf("The remainder is %d\n",remainder);
printf("The cat is %d\n",quotient);
//receive and print the size of the file,the quotient and the remainder           
for (int i = 0; i < quotient; i++) {
    recv(client_socket,containerOFmode,sizeof(containerOFmode),0);
    bytes_transferred += sizeof(containerOFmode);
    fwrite(containerOFmode,sizeof(char),pFILETOWRITE);
    printf("%s\n",containerOFmode);
    printf("The size of this send was:%d\n",sizeof(containerOFmode));
    printf("Bytes transferred so far:%d\n",bytes_transferred);
    bzero(containerOFmode,sizeof(containerOFmode));
    /*
        for each iteration receive the 1024 bytes and write it to the pFILETOWRITE,while also being verbose to the console
    */
}
recv(client_socket,remainder. 0);
bytes_transferred += remainder;
fwrite(containerOFmode,pFILETOWRITE);
printf("%s\n",containerOFmode);
printf("The size of this send was:%d\n",remainder);
printf("Bytes transferred so far:%d\n",bytes_transferred);
bzero(containerOFmode,sizeof(containerOFmode));
/*
        receive the remaining bytes and write it to the pFILETOWRITE,while also being verbose to the console
*/
fclose(pFILETOWRITE);
goto jump;//                                                                                                 

问题在于，对于超过 10 MB 左右的大文件，视频或可执行文件会损坏。我不知道为什么会发生这种情况，任何帮助将不胜感激。

解决方法

您的代码中的主要问题是您假设 B.graphql 和 send() 总是成功并发送和/或接收请求的总字节数。这是不正确的：您必须检查这些函数的返回值并采取相应措施。

还有其他问题，但您没有发布可编译的程序，因此缺少大量代码以进行更完整的分析。