Weird characters outputting in server side - c

Question

I have a bunch of weird characters in my output file when I send it from the client to the server. When I stream the server into an array and print it out, it looks good and legible. However, when I send it over to the server, I get a bunch of weird characters and MICROSOFT everywhere in the text document. Anybody know what's wrong?
Client:
if(sendSize <=0){
for(;;){
unsignedchar buff[256]={0};
int nread = fread(buff,1,256, fp);
total = total + nread;
percentage =(total / fFileSize)*100;
printf("\r%s: Percentage sent: %.2f", NAME_C, percentage);
/* Send data in 256 byte chunks */
if(nread >0){
send(clientSock, buff, nread, 0);
}
if(nread <256){
if(feof(fp)){
printf("\nSend Success!\n");
break;
}
}
}
//printf("%.2f", total);
}
Server:
/* Receive data from client */
char* fileName ="test.txt";
FILE*fp = fopen(fileName,"w+");;
float total =0;
float bytesReceived;
unsignedchar buff[256]={0};
float percentage =(bytesReceived / total)*100;
while((bytesReceived = recv(listenSock, buff,sizeof(buff),0))<0){
//bytesReceived = recv(listenSock, buff, 256, 0);
if(bytesReceived >0){
printf("DONE");
}
//total = total + bytesReceived;
fwrite(buff,sizeof(char), bytesReceived, fp);
//printf("\r%s: Percentage received: %.2f", NAME_C, percentage);
}

Answer 1

Your server's recv() loop is using <0 when it should be using >0 instead. recv() returns -1 on error, 0 on graceful disconnect, and >0 on bytes received.
Also, is listenSock the actual listening socket, or the socket returned by accept()? You should be passing the latter to recv(). My guess is that you are passing the former instead, causing recv() to fail and return -1, which you then enter the body of the loop with garbage buff data and a bad bytesReceived value. The third parameter of fwrite() is a size_t, which is an unsigned type, so passing a signed value of -1 will get interpreted as an unsigned value of 4294967295 or even 18446744073709551615, depending on the size of size_t. Either way, you would be writing garbage to your file, or even crashing the code trying to access invalid memory.
There are other minor issues with your code as well. Try something more like this instead:
Client:
if(sendSize <=0){
unsigned char buff[256];
do{
int nread = fread(buff, sizeof(char), 256, fp);
if (nread > 0){
total += nread;
percentage = (total / fFileSize)*100;
printf("\r%s: Percentage sent: %.2f", NAME_C, percentage);
/* Send data in 256 byte chunks */
if (send(clientSock, buff, nread, 0) == -1){
printf("\nSend Failed!\n");
break;
}
}
if (nread != 256){
if (feof(fp)){
printf("\nSend Success!\n");
else
printf("\nRead Failed!\n");
break;
}
}
while (1);
//printf("%.2f", total);
}
Server:
/* Receive data from client */
char* fileName = "test.txt";
FILE* fp = fopen(fileName, "wb+");
if (!fp){
printf("\nOpen Failed!\n");
}
else{
float total = 0;
float percentage = 0;
int bytesReceived;
unsigned char buff[256];
do{
bytesReceived = recv(acceptedSock, buff, sizeof(buff), 0);
if (bytesReceived <= 0){
if (bytesReceived < 0){
printf("\nRecv Failed!\n");
}
else{
printf("\nDisconnected!\n");
}
break;
}
//total += bytesReceived;
//percentage = ...
if (fwrite(buff, sizeof(char), bytesReceived, fp) != bytesReceived){
printf("\nWrite Failed!\n");
break;
}
//printf("\n%s: Percentage received: %.2f", NAME_C, percentage);
}
while (1);
}