TCP Programming Gotchas
By Noah Davids, October 01, 2002
Programs that don't properly parse TCP-based messages may exhibit random failures that can be hard to detect. Noah provides some insights to avoid random TCP parsing errors.
Listing 1: Parsing AL messages from a TCP byte stream.
Listing 2: Test your application by sending randomly selected lengths of multiple
AL messages from a buffer.
int send_msg (fd, bp)
int fd;
char *bp;
{
static char stream_buffer [MAX_MSG_LEN * MAX_MSGS];
static msg_count = 0;
char * cp;
int stream_len = 0;
int count, saved_count, sent;
if (msg_count == 0)
stream_buffer [0] = 0x0;
strcat (stream_buffer, bp);
msg_count++;
if (msg_count < MAX_MSGS)
if ((random () * MAX_MSGS) > msg_count)
return (0);
stream_len = strlen (stream_buffer);
cp = stream_buffer;
while (stream_len > 0)/
{
count = random () * stream_len;
if (count == 0)
count = 1;
saved_count = count;
sent = 0;
while (sent != count)
{
sent = send (fd, cp, count, 0);
if (sent < 1)
return (-1);
if (sent < count)
{
cp = &cp [sent];
count = count - sent;
}
}
cp = &cp [count];
stream_len = stream_len - saved_count;
count = random () * 5;
sleep (count);
}
msg_count = 0;
return (1);
}
