winsock recv function recieve garbage in between relevant data - c

Question

I'm in the making of a TCP client-server program that sends data from the server to the client (this works fine) and then echos it back to the server (doesn't work fine). when using the recv function, the first time I receive data works well but after that a lot of garbage comes in, the data itself comes as well but in the middle of a lot of garbage, both the recv/send return values are always correct. besides that the first time I start the testing of this program after starting the computer is much better (usually works). Does anyone have a idea about the why's? I believe some buffer fills up or the recv stops being a blocking function somehow...
Thanks in advance...
this is the Client's code:
for(i=0;i<FIRSTSENDING;i++)
//the buffer is a chained-list with 4 fields per struct ( x,y,z,time )
{
for(j=0;j<NUMBEROFVARIABLES;j++)
{
while(head->data[j][0]!='b'); //the data has a 'b' at first and 'e'
in the end.
b1 = send(t,head->data[j],strlen(head->data[j]),0);
}
while(head->general[0]!='b');
b1 = send(t,head->general,strlen(head->general),0);
temp = head;
head = head->next;
free(temp);
}
the code for the server is:
for(i=0;i<FIRSTSENDING;i++)
{
for(j=0;j<NUMBEROFVARIABLES;j++)
{
newDatagram->data[j][0]=0;
a = recv(s,reci, LENGTHVARAIBLE , 0);
strcpy(newDatagram->data[j],reci);
newDatagram->data[j][LENGTHVARAIBLE] = 0;
}
newDatagram->general[0]=0;
a = recv(s,reci, LENGTHTIME , 0);
strcpy(newDatagram->general,reci);
newDatagram->general[LENGTHTIME] = 0;
_ftime(&timebuffer);
//fixing the time and sending it
timer=(double)(timebuffer.millitm)/1000+timebuffer.time;
newDatagram->general[LENGTHTIME-1]=0;
pointerTime = &newDatagram->general[1];
if(newDatagram->general[0]=='b')
{
attol=std::stod(pointerTime);
if((timer-attol)>delay1)
delay1=timer-attol;
}
}
delay1=delay1/10*15*1000; //adding 10 percent and making milli the right delay
delay=(int)(delay1);
delay=delay% 100000;
nextDelay=delay;
printf("The first delay is: %d in milliseconds\n",delay); //This is an incriment of 10% to the delay.
the code finds the max delay for those runs and shows it.

Answer 1

a = recv(s,reci, LENGTHVARAIBLE , 0);
strcpy(newDatagram->data[j],reci);
This is not correct: strcpy expects the buffer to be a null-terminated string, but you do not send the terminating null byte. So strcpy reads more data from the buffer than recv fills in. Here is where the garbage comes from.
And even if you send the terminating null byte, you cannot guarantee that recv reads the whole message at once, or that it doesn't merge several messages in a single one (there are no any message boundaries in stream sockets).
You should use exactly a bytes after each recv (and maybe use memcpy instead of strcpy). To determine where a message ends, you can either send the zero byte and look for this byte at receiving side (note that you can get more than one message in a single recv call), or prepend each message with a fixed-length header containing the length of message.