C套接字下载函数传输损坏的文件

Question

我正在尝试在C套接字中实现下载。这个想法是在客户端中获取文件的大小，并一次、多次发送1024个字节，然后发送剩余的字节。在服务器端，您将接收这些字节，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, 1, 1024, pLOCALFILE);
send(sock, container, sizeof(container) , 0);
memset(container, 0, 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, 1, remainder, pLOCALFILE);
send(sock, container, remainder, 0);
memset(container, 0, sizeof(container));
fclose(pLOCALFILE);

这是服务器代码

char filename[260];
get_string_between_spaces(filename, buffer, sizeof(buffer), 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("%sn", 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 %dn", remainder);
printf("The cat is %dn", 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), sizeof(containerOFmode), pFILETOWRITE);
printf("%sn", containerOFmode);
printf("The size of this send was:%dn", sizeof(containerOFmode));
printf("Bytes transferred so far:%dn", 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, containerOFmode, remainder. 0);
bytes_transferred += remainder;
fwrite(containerOFmode, sizeof(char), remainder, pFILETOWRITE);
printf("%sn", containerOFmode);
printf("The size of this send was:%dn", remainder);
printf("Bytes transferred so far:%dn", 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;//                                                                                                 

问题是，对于超过10MB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，任何帮助都将不胜感激。

Answer 1

代码中的主要问题是假设send()和recv()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的行动。

还有其他问题，但你没有发布一个可编译的程序，所以为了进行更完整的分析，缺少了很多代码。