Sending large data package with TCP - winsock

Question

A small struct is sent beforehand to the client that specifies package_size amount of data should be received which is what p->data_value_1 contains.

Server side:

void Server::sendDataSingleUser(char *data_in, int user, unsigned int package_size){
 package_size_sent_ = 0;
 FD_ZERO(&write_set_);
 FD_SET(sockets_[user], &write_set_);
 while(package_size_sent_ < package_size){
 timeout_.tv_sec = 3;
 timeout_.tv_usec = 0;
 i_result_ = select(0, 0, &write_set_, 0, &timeout_);
 // Socket free, send a package
 if(i_result_ > 0){
 i_result_ = send(sockets_[num_clients_], data_in+package_size_sent_, package_size - package_size_sent_, 0);
 // Move buffer pointer
 if(i_result_ > 0){
 package_size_sent_ += i_result_;
 }
 // send error
 if(i_result_ == SOCKET_ERROR){
 // Handle the error
 }
 }
 // Socket still bussy
 else{
 // Disconnect the client
 }
 }
}

Client side:

*size_p = new char[(unsigned int)p->data_value_1];
int temp_count = 0, data_received, package_size = p->data_value_1;
while(temp_count < package_size){
 data_received = recv(connect_socket_, size_p+temp_count, package_size - temp_count, 0);
 // Move buffer pointer
 if(data_received > 0){
 temp_count += data_received;
 }
}

What can be improved/what's incorrect?

Answer 1

In both read and write you should leave the loop after an error (unless you have explicitly tested and fixed the error).

while(totalRecieved < readSize)
{
 dataRecieved = recv(socket, date + totalRecieved, readSize - totalRecieved);
 if (dataRecieved > 0)
 {
 totalRecieved += dataRecieved;
 continue;
 }
 if ((dataRecieved == -1) && (errno == EAGAIN || errno == EWOULDBLOCK))
 {
 // Simple error just try again.
 continue;
 }
 if (dataRecieved == -1 && errno == EINTR)
 {
 // An interrupt was received.
 // This is usually a signal by another thread to give up
 // but you can ignore it if you want.
 continue;
 }
 // Any other error is bad.
 // looping is just going to cause infinite loops.
 break;
}
if (totalRecieved < readSize)
{
 // BAD THINGS HAVE HAPPENED
}

• David S: Think I got it fixed up in the server part(if an error occurs it closes the clients socket and then calls return. Will add the check to the client part, thanks!