How to turn a character array into uint8_t

c casting send recv uint8t
fatalError picture fatalError · Nov 14, 2016 · Viewed 18.3k times · Source

I have a server-client application that I'm working on that basically simulates a chat room. This is an assignment for school and the protocol specifications are somewhat strict.

I have a char array which will store all messages from a client.

The client must first send the length of the message as a uint8_t and then the message itself as a char array.

My problem is I need to store the uint8_t value that is sent before the actual message is sent but I can only use the message array to store any information coming from the client.

If I'm not mistaken the char array will not store the uint8_t that gets sent over unless I cast it somehow.

How can I convert the uint8_t to characters and back to uint8_t?

I've tried looking for a similar problem on here but couldn't find an example.

server.c 

char msg[100];
recv(clients_sd, msg, sizeof(msg), 0);
uint8_t len; /* store the length of the message here */
char message_received[len];
recv(clients_sd, message_received, sizeof(message_received), 0); /* get and store the message here */

client.c

uint8_t length = 21;
char clients_message[] = "Hi how are you today?";
send(servers_sd, &length, sizeof(length), 0);
send(serers_sd, &clients_message, sizeof(clients_message), 0);

Answer

PSkocik picture PSkocik · Nov 14, 2016

If you're on an architecture where uint8_t is a typedef to unsigned char (you most likely are), then simply take the first char and cast it to uint8_t:

length = (uint8_t)(message_received[0]);

It should work.

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