c，c 语言，网络编程

socket-server.cpp

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <string>
#include <iostream>
#include <climits>
#define LENGTH 10
#define SIZE 128
struct socketaddr {
  unsigned short sa_family;
  char sa_data[14];
};
struct socketaddr_in {
  short int sin_family;
  unsigned short int sin_port;
  struct in_addr sin_addr;
  unsigned char sin_zero[8];
};
int String2int(char *str) {
  char flag = '+';
  long res = 0;
  if (*str == '-') {
    ++str; // 指针指向下一个
    flag = '-';
  }
  while (*str >= 48 && *str <= 57)
  {
    res = 10 * res + *str++ - 48;
  }
  if (flag == '-') {
    res = -res;
  }
  return (int) res;
}
int main(int argc, char **argv){
  using namespace std;
  // socketaddr addr;
  cout << "socket start" << endl;
  cout << "int size:" << sizeof(int) << endl;
  cout << "class socketaddr size:" << sizeof(socketaddr) << endl;
  cout << "class socketaddr_in size:" << sizeof(socketaddr_in) << endl;
  cout << "class in_addr size:" << sizeof(in_addr) << endl;
  int serv_port;
  if (argc != 2) {
    cout << "参数错误" << endl;
    exit(1);
  }
  serv_port = String2int(argv[1]);
  cout << "端口号：" << serv_port << endl;
  int res;
  int socketfd;
  int clientfd;
  struct socketaddr_in hostaddr;
  struct socketaddr_in clientaddr;
  unsigned int addrlen;
  char buf[SIZE];
  int cnt;
  cout << "创建服务器套接字 socket" << endl;
  cout << "AF_INET:" << AF_INET << endl;
  cout << "SOCK_STREAM:" << SOCK_STREAM << endl;
  socketfd = socket(AF_INET, SOCK_STREAM, 0);
  if (socketfd == -1) {
    cout << "创建服务器套接字失败" << endl;
    exit(1);
  }
  cout << "绑定协议号与端口号" << endl;
  hostaddr.sin_family = AF_INET;
  hostaddr.sin_port = htons(serv_port);
  cout << "本机IP地址" << INADDR_ANY << endl;
  hostaddr.sin_addr.s_addr = INADDR_ANY;
  bzero(&(hostaddr.sin_zero), 8);
  // 1.一个应用程序只能绑定一个端口(一个套接字只能绑定一个端口)
  // 2.UDP端口和TCP端口 虽然端口号相同，但是是不同的端口
  /*
     3.病毒端口复用，是先断开原来的端口，然后自己连接上去，然后是自己的数据就自>己处理
    不是自己的就分发给其他程序
  */
  // 4.可以多个线程同时receive你绑定的套接字，共享你绑定的套接字
  /*
     5.设置端口复用
     SO_REUSEADDR可以用在以下4种情况下
        5.1当有一个socket1处于TIME_WAIT状态时，而你启动的程序socket2需要用到该地址和端口，你的程序可以用到此项。
        5.2SO_REUSEADDR允许同一个port上启动同一服务的多个实例(多个进程)。但每个>实例绑定的ip地址不能相同。有多块网卡或用IP Alias技术的机器可以测试这种情况。
        5.3SO_REUSEADDR允许单个进程绑定相同的端口到多个socket上，但每个socket绑>定的ip地址不同，这和5.2很相似，区别请看UNPv1
        5.4SO_REUSEADDR允许完全相同的地址和端口绑定，但这只用于UDP的多播，不能用于TCP。
    注意：设置端口复用函数要在绑定之前调用，而且只要绑定到同一个端口的所有套接字都得设置复用。
  */
  // int opt = 1;
  // setsockopt(socketfd, SOL_SOCKET, SO_REUSEADDR, (const void *)&opt, sizeof(opt));
  res = bind(socketfd, (struct sockaddr *) &hostaddr, sizeof(struct sockaddr));
  if (res == -1) {
    cout << "套接字绑定失败" << endl;
    exit(1);
  }
  res = listen(socketfd, LENGTH);
  if (res == -1) {
    cout << "设置监听模式错误" << endl;
    exit(1);
  }
  cout << "等待客户端请求连接" << endl;
  while (1) {
    addrlen = sizeof(struct socketaddr_in);
    clientfd = accept(socketfd, (struct sockaddr *) &clientaddr, &addrlen);
    if (clientfd == -1) {
      cout << "接受连接请求错误" << endl;
      continue;
    }
    cout << "客户端 IP" << inet_ntoa(clientaddr.sin_addr) << endl;
    cnt = recv(clientfd, buf, SIZE, 0);
    if (cnt == -1) {
        cout << "数据接收失败" << endl;
        exit(1);
    }
    cout << buf << endl;
    close(clientfd);
  }
  return 0;
}

socket-client.cpp

#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <string>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#define SIZE 128
struct socketaddr {
  unsigned short sa_family;
  char sa_data[14];
};
struct socketaddr_in {
  short int sin_family;
  unsigned short int sin_port;
  struct in_addr sin_addr;
  unsigned char sin_zero[8];
};
int String2int(char *str) {
  char flag = '+';
  long res = 0;
  if (*str == '-') {
    ++str; // 指针指向下一个
    flag = '-';
  }
  while (*str >= 48 && *str <= 57)
  {
    res = 10 * res + *str++ - 48;
  }
  if (flag == '-') {
    res = -res;
  }
  return (int) res;
}
int main(int argc, char **argv) {
  using namespace std;
  cout << argc << endl;
  cout << argv << endl;
  if (argc != 3) {
    cout << "参数错误" << endl;
    exit(1);
  }
  int res;
  int sockfd;
  struct socketaddr_in servaddr;
  char buf[SIZE];
  int cnt;
  int serv_port;
  serv_port = String2int(argv[1]);
  if (serv_port == 0) {
    cout << "端口错误" << endl;
    exit(1);
  }
  sockfd = socket(AF_INET, SOCK_STREAM, 0);
  if (sockfd == -1) {
    cout << "套接字创建失败" << endl;
    exit(1);
  }
  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons(serv_port);
  cout << "htons(...):" << htons(serv_port) << endl; 
  servaddr.sin_addr.s_addr = INADDR_ANY;
  bzero(&(servaddr.sin_zero), 8);
  res = connect(sockfd, (struct sockaddr *) &servaddr, sizeof(struct sockaddr));
  if (res == -1) {
    cout << "连接失败" << endl;
    exit(1);
  }
  strcpy(buf, argv[2]);
  cnt = send(sockfd, buf, SIZE, 0);
  if (cnt == -1) {
    cout << "发送失败" << endl;
    exit(1);
  }
  cout << "发送数据：" << buf << endl;
  close(sockfd);
  return 0;
}