如何测试Linux下tcp最大连接数限制详解

/*
 * g++ -o test_epoll ./test_epoll.c
 */
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

int SetReuseAddr(int fd)
{
 int optval = 1;
 socklen_t optlen = sizeof(optval);
 return setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &optval, optlen);
}

int main()
{
 int fd = socket(AF_INET, SOCK_STREAM, 0);
 int iRet = SetReuseAddr(fd);
 if (iRet != 0)
 {
 printf("setsockopt for SO_REUSEADDR failed, error:%s\n", strerror(iRet));
 return iRet;
 }

 struct sockaddr_in addr;
 memset(&addr, 0, sizeof(addr));
 addr.sin_family = AF_INET;
 addr.sin_port = htons(8080);
 addr.sin_addr.s_addr = INADDR_ANY;
 if (bind(fd, (struct sockaddr*)&addr, sizeof(addr)) == -1)
 {
 printf("bind failed, error:%s\n", strerror(errno));
 return errno;
 }

 if (listen(fd, 5) == -1)
 {
 printf("listen failed, error:%s\n", strerror(errno));
 return errno;
 }
 printf("Listening on 8080...\n");

 int epfd = epoll_create(102400);
 struct epoll_event event;
 event.events = EPOLLIN;
 event.data.fd = fd;
 epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &event);

 struct epoll_event revents[102400];
 int iOnline = 0;
 while (1)
 {
 int num = epoll_wait(epfd, revents, 102400, 60 * 1000);
 printf("epoll_wait return %d\n", num);
 if (num > 0)
 {
  for (int i = 0; i < num; i++)
  {
  if (revents[i].data.fd == fd)
  {
   int client;
   struct sockaddr_in cli_addr;
   socklen_t cli_addr_len = sizeof(cli_addr);
   client = accept(fd, (struct sockaddr*)&cli_addr, &cli_addr_len);
   if (client == -1)
   {
   printf("accept failed, error:%s\n", strerror(errno));
   if (errno == EMFILE)
   {
    printf("per-process limit reached\n");
    exit(errno);
   }
   if (errno == ENFILE)
   {
    printf("system-wide limit reached\n");
    exit(errno);
   }
   continue;
   }

   iOnline++;
   printf("Receive a new connection from %s:%d\n", inet_ntoa(cli_addr.sin_addr), cli_addr.sin_port);
   event.events = EPOLLIN;
   event.data.fd = client;
   epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &event);
  }
  }
 }
 printf("Online number:%d\n", iOnline);
 }

 return 0;
}

package main

import (
 "net"
 "fmt"
 "time"
 "strconv"
 "runtime"
)

func Connect(host string, port int) {
 _, err := net.Dial("tcp", host+":"+strconv.Itoa(port))
 if err != nil {
 fmt.Printf("Dial to %s:%d failed\n", host, port)
 return
 }

 for {
 time.Sleep(30 * 1000 * time.Millisecond)
 }
}

func main() {
 count := 0
 for {
 go Connect("192.168.63.128", 8080)
 count++;
 fmt.Printf("Gorutue num:%d\n", runtime.NumGoroutine())
 time.Sleep(100 * time.Millisecond)
 }
}

1 * soft nofile 102400
2 * hard nofile 102400