Question

could be any difference in solving errors between this two functions?:
To this question brought me another question … is number of characters always same as number of bytes?
For more info: I use it in C on Linux for TCP socket comunication(sys/socket.h)
Thanks for your responses.

send()
write()

Return:
write():
On success, the number of bytes written are returned (zero indicates nothing was written). On error, -1 is returned, and errno is set appropriately. If count is zero and the file descriptor refers to a regular file, 0 will be returned without causing any other effect. For a special file, the results are not portable.

send():
The calls return the number of characters sent, or -1 if an error occurred.

Question from stackoverflow which says that this methods should be same with using flag zero.
here

int client_sockfd;
char* msg;
int length = strlen(msg); 

//first option
if(send(client_sockfd, msg, length, 0) != length) return 1;
else return 0;
//second option 
if(write(client_sockfd, msg, length) != length) return 1;
else return 0;

Answer 1

They will both return the same number of written bytes (== characters in this case. EXCEPT note this:

If the message is too long to pass atomically through the underlying protocol, the
error EMSGSIZE is returned, and the message is not transmitted.

In other words, depending on the size of the data being written, write() may succeed where send() may fail.