Simple echo server with BIOs

[Brian Lavender]

I am trying to write a simple echo server. I first decided to try it
with the BIO without any keys. I keep having problems with blocking. It
seems that it gets stuck somewhere expecting a read or a write. You will
notice on the client that I do BIO_write. Then I do a BIO_read in a loop
to get the data. This comes across, but then when I try to do a
BIO_write the second time, it blocks and I get no return. What am
I doing wrong?

I have the OpenSSL book and it just has writes from the client and the
server just prints it out. Is there a simple example of an echo server
and client somewhere?

brian

=== simple_client.c ===

#include "openssl/ssl.h"
#include "openssl/bio.h"
#include "openssl/err.h"

#include "stdio.h"
#include "string.h"

int main()
{
BIO * bio;
int p;

char * request = "Some new things coming today\n";
char * request2 = "Tomorrow is a new day\n";
char r[1024];

/* Set up the library */

ERR_load_BIO_strings();
SSL_load_error_strings();
OpenSSL_add_all_algorithms();

/* Create and setup the connection */

bio = BIO_new_connect("mary.internal.brie.com:4422");
if(bio == NULL) { printf("BIO is null\n"); return; }

if(BIO_do_connect(bio) <= 0)
{
ERR_print_errors_fp(stderr);
BIO_free_all(bio);
return;
}

/* Send the request */

BIO_write(bio, request, strlen(request));
for(;;)
{
p = BIO_read(bio, r, 1023);
if(p <= 0) break;
r[p] = 0;
printf("%s", r);
}

BIO_flush(bio);

if (BIO_should_read(bio))
printf("Bio needs to read\n");

BIO_write(bio, request2, strlen(request2));

/* Read in the response */

for(;;)
{
p = BIO_read(bio, r, 1023);
if(p <= 0) break;
r[p] = 0;
printf("%s", r);
}

/* Close the connection and free the context */

BIO_free_all(bio);
return 0;
}

=== simple_server.c ===

#include "stdio.h"
#include "string.h"

#include "openssl/bio.h"
#include "openssl/ssl.h"
#include "openssl/err.h"
#define BUFSIZE 1024

int main()
{
BIO *abio, *out ;
pthread_t tid;
char buf[80];
int err, nread;

printf("Secure Programming with the OpenSSL API, Part 4:\n");
printf("Serving it up in a secure manner\n\n");

SSL_library_init();

SSL_load_error_strings();
ERR_load_BIO_strings();
ERR_load_SSL_strings();
OpenSSL_add_all_algorithms();

printf("Attempting to create BIO object... ");

abio = BIO_new_accept("4422");

printf("Waiting for incoming connection...\n");

if(BIO_do_accept(abio) <= 0)
{
ERR_print_errors_fp(stdout);
BIO_free_all(abio);
return -1;
}

if (BIO_do_accept(abio) <= 0)
{
ERR_print_errors_fp(stderr);
BIO_free_all(abio);
return -1;
}
printf("Got a connection\n");

out = BIO_pop(abio);

do
{
for (nread = 0; nread < sizeof(buf); nread += err)
{
err = BIO_read(out, buf + nread, sizeof(buf) - nread);
printf("The number of bytes read %d\n",err);
if (BIO_should_retry(out) )
printf("Should retry read\n");
if (err <= 0)
break;

if ( err > 0 )
{
BIO_puts(out,"Hello from the server\n");
BIO_write(out,buf,err);
fprintf(stdout, "%s", buf);
}
}
}
while (err > 0);

if (err < 0)
printf("Error on read\n");

// replacement ends here

BIO_free_all(abio);

}

--
Brian Lavender
http://www.brie.com/brian/
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