File partially sent in c - c

Question

I'm trying to send files using TCP from a windows client to a Linux server in C.
The size of the buffer I use to send the data is 65535. When the size of the file exceeds this value, I get an error saying 'connection reset by peer' or the error code 10054. When the size of the file is less than 65535 bytes, the server receives only a part of it (usually 2760 bytes).
I just want to send files with a maximum size of 50 MB.
This is the part of the windows client that I use to send data:
char *fileName; // pointer to filename
char buf[65535]; // buffer
int fileSize; // # bytes to send
for(i = 0; i < ARRAYSIZE; i++) {
if(selectList[i] != NULL) {
// select file
fileName= selectList[i]; // get path and filename from selectList
printf("=============================================\nSending: %s\n", fileName);
filefd = fopen(fileName, "rb"); // open file
if(filefd == NULL) {
printf("File %s not found\n", fileName);
exit(1);
}
// read and send file
memset(buf, '\0', 65535);
while((fileSize= fread(buf, sizeof(char), 65535, filefd)) > 0) { // read file
if((numberOfBytes = send(sockfd, buf, fileSize, 0)) < 0) { // send buffer
printf("send: %s (Error: %d)\n", filename, WSAGetLastError());
break;
}
printf("#bytes = %i \n", numberOfBytes);
memset(buf, '\0', 65535);
}
printf("File %s send!\n", filename);
// close file after sending it
if(fclose(filefd) < 0) {
printf("fclose: %i", WSAGetLastError());
}
} else if(selectList[0] == NULL) {
printf("no files selected");
}
}
The selectList contains multiple strings such as: C:\Windows\test.txt
The recieve part of the Linux server:
char* fr_name = "/home/MtFS/UploadedFiles/public/testFile.gif";
FILE *fr = fopen(fr_name, "wb");
if(fr == NULL)
printf("[Open_File]file %s cannot be created\n", fr_name);
else {
bzero(revbuf, LENGTH);
int fr_block_sz = 0;
while((fr_block_sz = recv(nsockfd, revbuf, LENGTH, 0)) > 0) {
int write_sz = fwrite(revbuf, sizeof(char), fr_block_sz, fr);
if(write_sz < fr_block_sz) {
error("[Write] error\n");
}
bzero(revbuf, LENGTH);
if (fr_block_sz == 0 || fr_block_sz != 512) {
break;
}
}
if(fr_block_sz < 0) {
if (errno == EAGAIN) {
printf("[Receive] time out\n");
}
else {
printf("[Receive] error\n");
exit(1);
}
}
printf("[Receive] succesfull\n");
fclose(fr);
}
What am I doing wrong?

Answer 1

Your problem are those 3 lines of code. That's not the correct way to know that you're done:
if (fr_block_sz == 0 || fr_block_sz != 512) {
break;
}
Also you check against 512 instead of LENGTH. But only 0 means that you're done (assuming your connection is not NONBLOCKED.)
As a side note: you do not have to clear your buffers (bzero, memset) before using them with a read since the read/recv will overwrite the content of the buffers anyway.

Answer 2

I think the culprit is this line in your server
if (fr_block_sz == 0 || fr_block_sz != 512) {
fr_block_sz cab be anything between 1 to 65535 - the size block that you sent.
In your code, when its not 512 so your server is terminating the connection.