299int main(int ac, char **av)

300{

301 if (ac != 2)

302 {

303 write(2, "Wrong number of arguments\n", 26);

304 exit(1);

305 }

306

307 g_listen_fd = socket(AF_INET, SOCK_STREAM, 0);

308 if (g_listen_fd < 0)

309 fatal();

310

311 struct sockaddr_in addr;

312 bzero(&addr, sizeof(addr));

313 addr.sin_family = AF_INET;

314 addr.sin_addr.s_addr = htonl(0x7f000001);

315 addr.sin_port = htons(atoi(av[1]));

316 if (bind(g_listen_fd, (const struct sockaddr *)&addr, sizeof(addr)) < 0)

317 fatal();

318 if (listen(g_listen_fd, 128) < 0)

319 fatal();

320

321 FD_ZERO(&g_activefds);

322 FD_SET(g_listen_fd, &g_activefds);

323 g_maxfd = g_listen_fd;

324 g_next_id = 0;

325 bzero(g_ids, sizeof(g_ids));

326 bzero(g_msgs, sizeof(g_msgs));

327

328 while (1)

329 {

330 g_readfds = g_writefds = g_activefds;

331 if (select(g_maxfd + 1, &g_readfds, &g_writefds, NULL, NULL) < 0)

332 continue;

333

334 for (int fd = 0; fd <= g_maxfd; fd++)

335 {

336 if (!FD_ISSET(fd, &g_readfds))

337 continue;

338 if (fd == g_listen_fd)

339 accept_client();

340 else

341 receive_from(fd);

342 break;

343 }

344 }

345 return 0;

346}

358static void fatal(void)

359{

360 write(2, "Fatal error\n", 12);

361 exit(1);

362}

379static void accept_client(void)

380{

381 struct sockaddr_in cli;

382 socklen_t clen = sizeof(cli);

383 int cfd = accept(g_listen_fd, (struct sockaddr *)&cli, &clen);

384 if (cfd < 0)

385 fatal();

386 if (cfd > g_maxfd)

387 g_maxfd = cfd;

388 g_ids[cfd] = g_next_id++;

389 g_msgs[cfd] = NULL;

390 FD_SET(cfd, &g_activefds);

391 sprintf(g_buf_write, "server: client %d just arrived\n", g_ids[cfd]);

392 send_all(cfd);

393}

415static void receive_from(int fd)

416{

417 int r = recv(fd, g_buf_read, 4096, 0);

418 if (r <= 0)

419 {

420 disconnect_client(fd);

421 return;

422 }

423 g_buf_read[r] = '\0';

424 g_msgs[fd] = str_join(g_msgs[fd], g_buf_read);

425

426 char *msg;

427 while (extract_message(&g_msgs[fd], &msg))

428 {

429 sprintf(g_buf_write, "client %d: %s", g_ids[fd], msg);

430 send_all(fd);

431 free(msg);

432 }

433}

451static void send_all(int except)

452{

453 int len = strlen(g_buf_write);

454 for (int fd = 0; fd <= g_maxfd; fd++)

455 {

456 if (fd == g_listen_fd || fd == except)

457 continue;

458 if (FD_ISSET(fd, &g_writefds))

459 send(fd, g_buf_write, len, 0);

460 }

461}

478static void disconnect_client(int fd)

479{

480 sprintf(g_buf_write, "server: client %d just left\n", g_ids[fd]);

481 FD_CLR(fd, &g_activefds);

482 close(fd);

483 send_all(fd);

484 free(g_msgs[fd]);

485 g_msgs[fd] = NULL;

486}

507static char *str_join(char *buf, char *add)

508{

509 int len = (buf ? (int)strlen(buf) : 0) + (int)strlen(add) + 1;

510 char *res = malloc(len);

511 if (!res)

512 fatal();

513 res[0] = '\0';

514 if (buf)

515 strcat(res, buf);

516 free(buf);

517 strcat(res, add);

518 return res;

519}

539static int extract_message(char **buf, char **msg)

540{

541 *msg = NULL;

542 if (!*buf)

543 return 0;

544 for (int i = 0; (*buf)[i]; i++)

545 {

546 if ((*buf)[i] == '\n')

547 {

548 char *newbuf = calloc(strlen(*buf + i + 1) + 1, sizeof(char));

549 if (!newbuf)

550 fatal();

551 strcpy(newbuf, *buf + i + 1);

552 *msg = *buf;

553 (*msg)[i + 1] = '\0';

554 *buf = newbuf;

555 return 1;

556 }

557 }

558 return 0;

559}