text: /* This example code is placed in the public domain. */
  
  #ifdef HAVE_CONFIG_H
  #include <config.h>
  #endif
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <errno.h>
  #include <sys/types.h>
  #include <sys/socket.h>
  #include <arpa/inet.h>
  #include <netinet/in.h>
  #include <string.h>
  #include <unistd.h>
  #include <gnutls/gnutls.h>
  
  #define SRP_PASSWD "tpasswd"
  #define SRP_PASSWD_CONF "tpasswd.conf"
  
  #define KEYFILE "key.pem"
  #define CERTFILE "cert.pem"
  #define CAFILE "/etc/ssl/certs/ca-certificates.crt"
  
  /* This is a sample TLS-SRP echo server.
   */
  
  #define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);}
  #define MAX_BUF 1024
  #define PORT 5556               /* listen to 5556 port */
  
  int main(void)
  {
          int err, listen_sd;
          int sd, ret;
          struct sockaddr_in sa_serv;
          struct sockaddr_in sa_cli;
          socklen_t client_len;
          char topbuf[512];
          gnutls_session_t session;
          gnutls_srp_server_credentials_t srp_cred;
          gnutls_certificate_credentials_t cert_cred;
          char buffer[MAX_BUF + 1];
          int optval = 1;
          char name[256];
  
          strcpy(name, "Echo Server");
  
          gnutls_global_init();
  
          /* SRP_PASSWD a password file (created with the included srptool utility) 
           */
          gnutls_srp_allocate_server_credentials(&srp_cred);
          gnutls_srp_set_server_credentials_file(srp_cred, SRP_PASSWD,
                                                 SRP_PASSWD_CONF);
  
          gnutls_certificate_allocate_credentials(&cert_cred);
          gnutls_certificate_set_x509_trust_file(cert_cred, CAFILE,
                                                 GNUTLS_X509_FMT_PEM);
          gnutls_certificate_set_x509_key_file(cert_cred, CERTFILE, KEYFILE,
                                               GNUTLS_X509_FMT_PEM);
  
          /* TCP socket operations
           */
          listen_sd = socket(AF_INET, SOCK_STREAM, 0);
          SOCKET_ERR(listen_sd, "socket");
  
          memset(&sa_serv, '\0', sizeof(sa_serv));
          sa_serv.sin_family = AF_INET;
          sa_serv.sin_addr.s_addr = INADDR_ANY;
          sa_serv.sin_port = htons(PORT); /* Server Port number */
  
          setsockopt(listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval,
                     sizeof(int));
  
          err =
              bind(listen_sd, (struct sockaddr *) &sa_serv, sizeof(sa_serv));
          SOCKET_ERR(err, "bind");
          err = listen(listen_sd, 1024);
          SOCKET_ERR(err, "listen");
  
          printf("%s ready. Listening to port '%d'.\n\n", name, PORT);
  
          client_len = sizeof(sa_cli);
          for (;;) {
                  gnutls_init(&session, GNUTLS_SERVER);
                  gnutls_priority_set_direct(session,
                                             "NORMAL:-KX-ALL:+SRP:+SRP-DSS:+SRP-RSA",
                                             NULL);
                  gnutls_credentials_set(session, GNUTLS_CRD_SRP, srp_cred);
                  /* for the certificate authenticated ciphersuites.
                   */
                  gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE,
                                         cert_cred);
  
                  /* request client certificate if any.
                   */
                  gnutls_certificate_server_set_request(session,
                                                        GNUTLS_CERT_IGNORE);
  
                  sd = accept(listen_sd, (struct sockaddr *) &sa_cli,
                              &client_len);
  
                  printf("- connection from %s, port %d\n",
                         inet_ntop(AF_INET, &sa_cli.sin_addr, topbuf,
                                   sizeof(topbuf)), ntohs(sa_cli.sin_port));
  
                  gnutls_transport_set_int(session, sd);
  
                  do {
                          ret = gnutls_handshake(session);
                  }
                  while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
  
                  if (ret < 0) {
                          close(sd);
                          gnutls_deinit(session);
                          fprintf(stderr,
                                  "*** Handshake has failed (%s)\n\n",
                                  gnutls_strerror(ret));
                          continue;
                  }
                  printf("- Handshake was completed\n");
                  printf("- User %s was connected\n",
                         gnutls_srp_server_get_username(session));
  
                  /* print_info(session); */
  
                  for (;;) {
                          ret = gnutls_record_recv(session, buffer, MAX_BUF);
  
                          if (ret == 0) {
                                  printf
                                      ("\n- Peer has closed the GnuTLS connection\n");
                                  break;
                          } else if (ret < 0
                                     && gnutls_error_is_fatal(ret) == 0) {
                                  fprintf(stderr, "*** Warning: %s\n",
                                          gnutls_strerror(ret));
                          } else if (ret < 0) {
                                  fprintf(stderr, "\n*** Received corrupted "
                                          "data(%d). Closing the connection.\n\n",
                                          ret);
                                  break;
                          } else if (ret > 0) {
                                  /* echo data back to the client
                                   */
                                  gnutls_record_send(session, buffer, ret);
                          }
                  }
                  printf("\n");
                  /* do not wait for the peer to close the connection. */
                  gnutls_bye(session, GNUTLS_SHUT_WR);
  
                  close(sd);
                  gnutls_deinit(session);
  
          }
          close(listen_sd);
  
          gnutls_srp_free_server_credentials(srp_cred);
          gnutls_certificate_free_credentials(cert_cred);
  
          gnutls_global_deinit();
  
          return 0;
  
  }
  