Problem - Kevin Tafuro

Instead, you should use this code from a thread, or use the traditional Unix model,
where you fork( ) off a new process for each client connection. Or you can simply
rearrange the code so that you incrementally read data without blocking.
unsigned char *spc_server_read(spc_ssock_t *ctx, size_t *len, size_t *end) {
unsigned char nonce[SPC_CWC_NONCE_LEN], status;
/* If it's the server's turn to speak, abort. We know it's the server's turn
* to speak if the first byte of the nonce is the CLIENT distinguisher.
*/
if (ctx->nonce[0] != SPC_SERVER_DISTINGUISHER &&
ctx->nonce[0] != SPC_SERVER_LACKS_NONCE) abort();
spc_get_status_and_nonce(ctx->fd, &status, nonce);
*end = status;
/* If we need to do so, copy over the random bytes of the nonce. */
if (ctx->nonce[0] == SPC_SERVER_LACKS_NONCE)
memcpy(ctx->nonce + SPC_IV_IX, nonce + SPC_IV_IX, SPC_IV_LEN);
/* Now, set the distinguisher field to client, and increment our copy of
* the nonce.
*/
ctx->nonce[0] = SPC_CLIENT_DISTINGUISHER;
spc_increment_counter(ctx->nonce + SPC_CTR_IX, SPC_CTR_LEN);
return spc_finish_decryption(ctx, status, nonce, len);
}
Now we just need to handle the server-side sending of messages, which requires only
a little bit of work:
void spc_ssock_server_send(spc_ssock_t *ctx, unsigned char *msg, size_t mlen) {
/* If it's not our turn to speak, abort. We know it's our turn if the client
* spoke last.
*/
if (ctx->nonce[0] != SPC_CLIENT_DISTINGUISHER) abort();
/* Set the distinguisher, but don't bump the counter, because we already did
* when we received the message from the client.
*/
ctx->nonce[0] = SPC_SERVER_DISTINGUISHER;
spc_base_send(ctx, msg, mlen);
}
There is one more potential issue that we should note. In some situations in which
you’re going to be dealing with incredibly long messages, it does not make sense to
have to know how much data is going to be in a message before you start to send it.
Doing so will require buffering up large amounts of data, which might not always be
possible, particularly in an embedded device.
500 | Chapter 9: Networking
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.