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

1. #include <arpa/inet.h>
   
2. #include <errno.h>
   
3. #include <netinet/in.h>
   
4. #include <signal.h>
   
5. #include <stdbool.h>
   
6. #include <stdio.h>
   
7. #include <stdlib.h>
   
8. #include <string.h>
   
9. #include <sys/capability.h>
   
10. #include <sys/socket.h>
    
11. #include <unistd.h>
    
12. static bool check_capability() {
    
13.   cap_t capabilities = cap_get_proc();
    
14.   bool result = false;
    
15.   do {
    
16.     if (capabilities == NULL) {
    
17.       perror("cap_get_proc");
    
18.       exit(EXIT_FAILURE);
    
19.     }
    
20.     cap_flag_value_t value;
    
21.     if (cap_get_flag(capabilities, CAP_NET_BIND_SERVICE, CAP_EFFECTIVE, &value) == -1) {
    
22.       perror("cap_get_flag");
    
23.       exit(EXIT_FAILURE);
    
24.     }
    
25.     if (value == CAP_SET) {
    
26.       result = true;
    
27.       break;
    
28.     }
    
29.     if (cap_get_flag(capabilities, CAP_NET_BIND_SERVICE, CAP_PERMITTED, &value) == -1) {
    
30.       perror("cap_get_flag");
    
31.       exit(EXIT_FAILURE);
    
32.     }
    
33.     if (value == CAP_CLEAR) {
    
34.       result = false;
    
35.       break;
    
36.     }
    
37.     cap_value_t caps[] = {CAP_NET_BIND_SERVICE};
    
38.     if (cap_set_flag(capabilities, CAP_EFFECTIVE, 1, caps, CAP_SET) == -1) {
    
39.       perror("cap_set_flag");
    
40.       exit(EXIT_FAILURE);
    
41.     }
    
42.     if (cap_set_proc(capabilities) == -1) {
    
43.       perror("cap_set_proc");
    
44.       exit(EXIT_FAILURE);
    
45.     }
    
46.     result = true;
    
47.   } while (false);
    
48.   cap_free(capabilities);
    
49.   return result;
    
50. }
    
51. static void deal_with_permission() {
    
52.   if (geteuid() == 0) {
    
53.     return;
    
54.   }
    
55.   if (check_capability() == false) {
    
56.   }
    
57.   if (check_capability() == false) {
    
58.     fprintf(stderr, "permission denied.\n");
    
59.     exit(EXIT_FAILURE);
    
60.   }
    
61. }
    
62. static void handler(int sig) { return; }
    
63. int main() {
    
64.   deal_with_permission();
    
65.   int fds[UINT16_MAX + 1];
    
66.   memset(fds, -1, sizeof(fds));
    
67.   struct sockaddr_in address = {.sin_family = AF_INET, .sin_port = 0, .sin_addr = {inet_addr("127.0.0.1")}};
    
68.   for (uint16_t i = 1; i != 0; i++) {
    
69.     address.sin_port = htons(i);
    
70.     fds[i] = socket(AF_INET, SOCK_STREAM, 0);
    
71.     int ret = bind(fds[i], (struct sockaddr *)&address, sizeof(address));
    
72.     if (ret == 0) {
    
73.       printf("bind (fd)%d -> (port)%d\n", fds[i], i);
    
74.     } else {
    
75.       printf("failed to bind to (port)%d: %s\n", i, strerror(errno));
    
76.       close(fds[i]);
    
77.       fds[i] = -1;
    
78.     }
    
79.   }
    
80.   signal(SIGINT, handler);
    
81.   printf("signal me (pid=%d) with SIGINT to cleanup, waiting...\n", getpid());
    
82.   pause();
    
83.   for (uint16_t i = 1; i != 0; i++) {
    
84.     if (fds[i] != -1) {
    
85.       close(fds[i]);
    
86.     }
    
87.   }
    
88.   return 0;
    
89. }

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