transfer files in a tcp threaded server C++ - c++

Question

Hi everyone i have a little problem, i supposed to transfer a file from a server( a tcp server with threads to a client). The problems appers at the end of transmision the file is recived by client but it stucks and I can't longer communicate with it.
This is the server
int main(int argc, char *argv[])
{
int socket_desc, client_sock, c;
struct sockaddr_in server, client;
//Create socket
socket_desc = socket(AF_INET, SOCK_STREAM, 0);
if (socket_desc == -1)
{
printf("Could not create socket");
}
puts("Socket created");
//Prepare the sockaddr_in structure
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(2025);
//Bind
if (bind(socket_desc, (struct sockaddr *) &server, sizeof(server)) < 0)
{
//print the error message
perror("bind failed. Error");
return 1;
}
puts("bind done");
//Listen
listen(socket_desc, 5);
//Accept and incoming connection
puts("Waiting for incoming connections...");
c = sizeof(struct sockaddr_in);
int enable = 1;
//Accept and incoming connection
puts("Waiting for incoming connections...");
c = sizeof(struct sockaddr_in);
pthread_t thread_id;
while ((client_sock = accept(socket_desc,
(struct sockaddr *) &client,
(socklen_t*) &c)))
{
puts("Connection accepted");
if (setsockopt(client_sock,
SOL_SOCKET,
SO_REUSEADDR,
&enable,
sizeof(int)) < 0)
error("setsockopt(SO_REUSEADDR) failed");
if (pthread_create(&thread_id,
NULL,
connection_handler,
(void*) &client_sock) < 0)
{
perror("could not create thread");
return 1;
}
//Now join the thread , so that we dont terminate before the thread
pthread_join(thread_id, NULL);
puts("Handler assigned");
}
if (client_sock < 0)
{
perror("accept failed");
return 1;
}
return 0;
}
void *connection_handler(void *socket_desc)
{
printf("Enter in handler");
//Get the socket descriptor
int sock = *(int*) socket_desc;
send_problemo(sock);
return 0;
}
This is the sending function where I think is the real problem
int send_problemo(int *sock)
{
ssize_t read_return;
char *file_path = "Problems/1.txt";
char buffer[BUFSIZ];
int filefd;
filefd = open(file_path, O_RDONLY);
char end[2] = "1";
if (filefd == -1)
{
perror("open");
exit (EXIT_FAILURE);
}
while (1)
{
read_return = read(filefd, buffer, BUFSIZ);
if (read_return == 0)
{
printf("este 0 \n");
break;
}
if (read_return == -1)
{
perror("read");
exit (EXIT_FAILURE);
}
if (write(sock, buffer, read_return) == -1)
{
perror("write");
exit (EXIT_FAILURE);
}
}
// close(sock);
close(filefd);
}
The client is connecting normally and receives the file in this function
int recive_problemo(int *sockfd)
{
char *file_path = "path.c";
char buffer[BUFSIZ];
ssize_t read_return;
int filefd;
filefd = open(file_path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
if (filefd == -1)
{
perror("open");
exit (EXIT_FAILURE);
}
do
{
read_return = read(sockfd, buffer, BUFSIZ);
if (read_return == -1)
{
perror("read");
exit (EXIT_FAILURE);
}
if (write(filefd, buffer, read_return) == -1)
{
perror("write");
exit (EXIT_FAILURE);
}
} while (read_return > 0);
close(filefd);
}
I kind of managed how to solve this. If i shutdown(SHUT_WR) from server the client isnt stuck anymore, but i want to communicate with it further.
Also with the same function if i transfer from client to server, it works perfectly, so can anyone help me please?

Answer 1

do
{
read_return = read(sockfd, buffer, BUFSIZ);
// error handling
// file write
} while (read_return > 0);
Will keep looping until the socket closes or there's an error. It has no way to tell if a file has finished.
Common solutions are to close the socket (but you don't want that) and establish a communication protocol so that you know when the file is done and can exit the loop.
To keep things very simple, I recommend sending the length of the file before sending the file. The loop now looks something like:
uint64_t file_len;
read_return = recv(sockfd, &file_len, sizeof(file_len), MSG_WAITALL);
if (read_return == sizeof(file_len))
{
// Strongly consider handling the endian of file_len here
while (file_len)
{
size_t readmax = std::min(file_len, BUFSIZ);
read_return = read(sockfd, buffer, readmax);
if (read_return > 0)
{
if (write(filefd, buffer, read_return) == -1)
{
perror("write");
exit (EXIT_FAILURE);
}
file_len -= read_return;
}
else
{
// handle error
// exit loop if not recoverable
}
}
}
The server end picks up the responsibility of getting and sending the length of the file. I won't get into that because there are too many different ways to get the length of a file. Pick your favourite.
Documentation on recv and MSG_WAITALL.