Dirty cli chatapp with C

client.c

#include <arpa/inet.h>
#include <err.h>
#include <math.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/socket.h>
#include <unistd.h>

#define PORT 1234

void *reader(void *arg) {
  int fd = *(int *)arg, lencache = 4;
  char buf[BUFSIZ] = {0};

  while (read(fd, buf, sizeof(buf)) > 0) {
    putchar('\r');
    for (int i = 0; i < lencache; i++)
      putchar(' ');

    printf("\r%s", buf);
    printf("You: ");
    fflush(stdout);

    lencache = strlen(buf) > 4 ? strlen(buf) : 4;
    bzero(buf, sizeof(buf));
  }
  return NULL;
}

int main(int argc, char **argv) {
  int fd = 0;
  char buf[BUFSIZ], msg[BUFSIZ];
  struct sockaddr_in sa = {};
  pthread_t thrd;

  if (argc != 3) {
    fprintf(stderr, "%s [IP] [NAME]\n", *argv);
    return (EXIT_FAILURE);
  }

  if ((fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    err(EXIT_FAILURE, "socket()");

  sa.sin_family = AF_INET;
  sa.sin_port = htons(PORT);
  if (!inet_pton(AF_INET, argv[1], &sa.sin_addr))
    err(EXIT_FAILURE, "inet_pton()");

  if (connect(fd, (const struct sockaddr *)&sa, sizeof(sa)))
    err(EXIT_FAILURE, "connect()");

  pthread_create(&thrd, NULL, reader, (void *)&fd);
  printf("You: ");

  while (fgets(msg, sizeof(msg), stdin)) {
    sprintf(buf, "%s: %s", argv[2], msg);
    write(fd, buf, strlen(buf));
    printf("You: ");

    bzero(buf, sizeof(buf));
    bzero(msg, sizeof(msg));
  }

  close(fd);
  return (EXIT_SUCCESS);
}

Makefile

CC = cc
DEBUG = -g -fsanitize=address -fno-omit-frame-pointer

SRC = $(wildcard *.c)
TARGETS = $(SRC:.c=)

all: $(TARGETS)

%: %.c
	$(CC) $(DEBUG) $< -o $@

clean:
	rm -rf $(TARGETS)

server.c

#include <arpa/inet.h>
#include <err.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/socket.h>
#include <unistd.h>

#define PORT 1234
#define LISTENQ 25

static int fds[LISTENQ] = {};

void *client_handler(void *arg) {
  int index = 0, n = 0, fd = *((int *)arg);
  char buf[BUFSIZ] = {0};

  for (int i = 0; i < LISTENQ; i++)
    if (fds[i] == fd) {
      index = i;
      break;
    }

  while ((n = read(fd, buf, sizeof(buf))) > 0) {
    for (int i = 0; i < LISTENQ; i++)
      if (fds[i] > 0 && fds[i] != fd) {
        write(fds[i], buf, strlen(buf));
      }

    bzero(buf, sizeof(buf));
  }

  if (n < 0)
    fprintf(stderr, "%d: read()", fd);

  fds[index] = 0;
  close(fd);
  return NULL;
}

int main(int argc, char **argv) {
  int fd = 0;
  struct sockaddr_in sa = {};
  pthread_t thrd;

  if ((fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    err(EXIT_FAILURE, "socket()");

  if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &(int){1}, sizeof(int)) < 0)
    err(EXIT_FAILURE, "setsockopt()");

  sa.sin_family = AF_INET;
  sa.sin_port = htons(PORT);
  sa.sin_addr.s_addr = htonl(INADDR_ANY);

  if (bind(fd, (const struct sockaddr *)&sa, sizeof(sa)))
    err(EXIT_FAILURE, "bind()");

  if (listen(fd, LISTENQ))
    err(EXIT_FAILURE, "listen()");

  while (true) {
    int p = 0, index = 0;

    for (int i = 0; i < LISTENQ; i++)
      if (!fds[i]) {
        index = i;
        break;
      }

    if ((fds[index] = accept(fd, (struct sockaddr *)NULL, NULL)) < 0) {
      perror("accept()");
      continue;
    }

    pthread_create(&thrd, NULL, client_handler, (void *)&fds[index]);
  }

  return (EXIT_SUCCESS);
}