端口

fishhh

假设我电脑性能最够的情况下，我开65536个应用[doge]
端口不复用，吧端口号全占了，这时在开应用会怎样

歌者文明清理员

不知道

小甲鱼的二师兄

端口被占了就不可用了

wp231957

我8G内存  开了300个浏览器窗口  就基本上 啥也干不了了   和崩溃没啥区别

dolly_yos2

不需要开65535个“应用”，一个进程就够用了，想知道具体会发生什么可以直接自己试试，这是 Linux 上能运行的代码，编译要链接 libcap（-lcap），需要 root 运行或者给 CAP_NET_BIND_SERVICE

#include <arpa/inet.h>
#include <errno.h>
#include <netinet/in.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/capability.h>
#include <sys/socket.h>
#include <unistd.h>
static bool check_capability() {
  cap_t capabilities = cap_get_proc();
  bool result = false;
  do {
    if (capabilities == NULL) {
      perror("cap_get_proc");
      exit(EXIT_FAILURE);
    }
    cap_flag_value_t value;
    if (cap_get_flag(capabilities, CAP_NET_BIND_SERVICE, CAP_EFFECTIVE, &value) == -1) {
      perror("cap_get_flag");
      exit(EXIT_FAILURE);
    }
    if (value == CAP_SET) {
      result = true;
      break;
    }
    if (cap_get_flag(capabilities, CAP_NET_BIND_SERVICE, CAP_PERMITTED, &value) == -1) {
      perror("cap_get_flag");
      exit(EXIT_FAILURE);
    }
    if (value == CAP_CLEAR) {
      result = false;
      break;
    }
    cap_value_t caps[] = {CAP_NET_BIND_SERVICE};
    if (cap_set_flag(capabilities, CAP_EFFECTIVE, 1, caps, CAP_SET) == -1) {
      perror("cap_set_flag");
      exit(EXIT_FAILURE);
    }
    if (cap_set_proc(capabilities) == -1) {
      perror("cap_set_proc");
      exit(EXIT_FAILURE);
    }
    result = true;
  } while (false);
  cap_free(capabilities);
  return result;
}
static void deal_with_permission() {
  if (geteuid() == 0) {
    return;
  }
  if (check_capability() == false) {
  }
  if (check_capability() == false) {
    fprintf(stderr, "permission denied.\n");
    exit(EXIT_FAILURE);
  }
}
static void handler(int sig) { return; }
int main() {
  deal_with_permission();
  int fds[UINT16_MAX + 1];
  memset(fds, -1, sizeof(fds));
  struct sockaddr_in address = {.sin_family = AF_INET, .sin_port = 0, .sin_addr = {inet_addr("127.0.0.1")}};
  for (uint16_t i = 1; i != 0; i++) {
    address.sin_port = htons(i);
    fds[i] = socket(AF_INET, SOCK_STREAM, 0);
    int ret = bind(fds[i], (struct sockaddr *)&address, sizeof(address));
    if (ret == 0) {
      printf("bind (fd)%d -> (port)%d\n", fds[i], i);
    } else {
      printf("failed to bind to (port)%d: %s\n", i, strerror(errno));
      close(fds[i]);
      fds[i] = -1;
    }
  }
  signal(SIGINT, handler);
  printf("signal me (pid=%d) with SIGINT to cleanup, waiting...\n", getpid());
  pause();
  for (uint16_t i = 1; i != 0; i++) {
    if (fds[i] != -1) {
      close(fds[i]);
    }
  }
  return 0;
}