I need help figuring out tcp sockets (clsocket) - c++

Question

I am having trouble figuring out sockets i am just asking the server for data at a position (glm::i64vec4) and expecting a response but the position gets way off when i get the response and the data for that position reflects that (aka my voxel game make a kinda cool looking but useless mess)
It's probably just me not understanding sockets whatsoever or maybe something weird with this library
one thought i had is it was maybe something to do with mismatching blocking and non blocking on the server and client
but when i switched the server to blocking (and put each client in a seperate thread from each other and the accepting process) it did nothing
if i'm doing something really stupid please tell me i know next to nothing about sockets
here is some code that probably looks horrible
Server Code
std::deque <CActiveSocket*> clients;
CPassiveSocket socket;
socket.Initialize();
socket.SetNonblocking();//I'm doing this so i don't need multiple threads for clients
socket.Listen("0.0.0.0",port);
while (1){
{
CActiveSocket* c;
if ((c = socket.Accept()) != NULL){
clients.emplace_back(c);
}
}
for (CActiveSocket*& c : clients){
c->Receive(sizeof(glm::i64vec4));
if (c->GetBytesReceived() == sizeof(glm::i64vec4)){
chkpkt chk;
chk.pos = *(glm::i64vec4*)c->GetData();
LOOP3D(chksize+2){
chk.data(i,j,k).val = chk.pos.y*chksize+j;
chk.data(i,j,k).id=0;
}
while (c->Send((uint8*)&chk,sizeof(chkpkt)) != sizeof(chkpkt)){}
}
}
}
Client Code
//v is a glm::i64vec4
//fsock is set to Blocking
if(fsock.Send((uint8*)&v,sizeof(glm::i64vec4)))
if (fsock.Receive(sizeof(chkpkt))){
tthread::lock_guard<tthread::fast_mutex> lock(wld->filemut);
wld->ichks[v]=(*(chkpkt*)fsock.GetData()).data;//i tried using the position i get back from the server to set this (instead of v) but that made it to where nothing loaded
//i checked it and the chunks position never lines up with what i sent
}

Answer 1

Without your complete application codes it's unrealistic to offer any suggestions of any particular lines of code correction.
But it seems like you are using this library. It doesn't matter if not, because most of time when doing network programming, socket's weird behavior make some problems somewhat universal. Thus there are a few suggestions for the portion of socket application in your project:
It suffices to have BLOCKING sockets.
Most of time socket's read have somewhat weird behavior, that is, it might not receive the requested size of bytes at a time. Due to this, you need to repeatedly call read until the receiving buffer is read thoroughly. For a complete and robust solution you can refer to Stevens's readn routine ([Ref.1], page122).
If you are using exactly the library mentioned above, you can see that your fsock.Receive eventually calls recv. And recv is just an variant of read[Ref.2], thus the solutions for both of them are just identical. And this pattern might help:
while(fsock.Receive(sizeof(chkpkt))>0)
{
// ...
}
Ref.1: https://mathcs.clarku.edu/~jbreecher/cs280/UNIX%20Network%20Programming(Volume1,3rd).pdf
Ref.2: https://man7.org/linux/man-pages/man2/recv.2.html#DESCRIPTION