设计程序
1．阅读TCP、UDP数据通信的例子8-2、8-7，理解并运行查看其功能。
2. 编写程序，使用socket网络接口函数，实现同一网段的两台主机的聊天。注：使用多线程，实现实时聊天功能。（使用UDP或TCP方式）

Server.cpp

#include <cstring>
#include <locale>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define BUFSIZE 4096
#define SERV_PORT 9528
#include <iostream>

using namespace std;

void sys_err(const char* str){
    perror(str);
    exit(1);
}

int main(){
    // listen fd
    int lfd = 0;
    // client fd
    int cfd = 0;
    char buf[BUFSIZE];

    // 创建服务端负责监听的socket
    lfd = socket(AF_INET, SOCK_STREAM, 0);

    // 设置服务端socket 地址结构
    struct sockaddr_in serv_addr;
    serv_addr.sin_family = AF_INET;
    // htons host to network short 主机字节序转网络字节序短整形 16位端口号
    serv_addr.sin_port = htons(SERV_PORT);
    // htonl host to network long 主机字节序转网络字节序长整形 32位IP地址
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    // 监听socket绑定地址结构
    if (bind(lfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1)
        sys_err("bind");

    // 设置监听上限
    listen(lfd, 128);

    // 阻塞监听
    struct sockaddr_in cli_addr; // 监听到的连接的地址结构的传出参数
    socklen_t cli_addr_len;
    cfd = accept(lfd, (struct sockaddr*)&cli_addr, &cli_addr_len);
    if (cfd == -1)
        sys_err("accept");
    // 打印连接信息
    char client_IP[40]; // IP字符串
    cout << "client connected..." << endl;
    printf("client ip : %s\n",inet_ntop(AF_INET, &cli_addr.sin_addr.s_addr, client_IP, sizeof(client_IP)));
    cout << "client port : " << ntohs(cli_addr.sin_port) << endl;


    // 处理
    while (1){
        // 读取客户端内容
        int len = read(cfd, buf, sizeof buf);

        if (len == 0){
            cout << "client disconnected..." << endl;
            break;
        }

        // 回显接受的客户端内容
        cout << "received client msg : " << buf << endl;

        for (int i = 0; i < len; i++)
            buf[i] = toupper(buf[i]);

        // 回复客户端
        write(cfd, buf, len);
    }

    close(lfd);
    close(cfd);

    return 0;
}

可以使用shell命令测试服务端代码

nc 127.0.0.1 9528

Client.cpp

#include <cstdlib>
#include <cstring>
#include <stdio.h>
#include <unistd.h>
#include <error.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <iostream>
#define BUFSIZE 4096
#define SERV_PORT 9528

using namespace std;

void sys_err(const char *str){
  perror(str);
  exit(1);
}

int main(){
  const char *serv_ip = "127.0.0.1"; // 要连接的服务器IP

  // 设置要连接的服务器的地址结构
  struct sockaddr_in serv_addr;
  serv_addr.sin_family = AF_INET;
  inet_pton(AF_INET, serv_ip, &serv_addr.sin_addr.s_addr);
  serv_addr.sin_port = htons(SERV_PORT);

  int cfd = socket(AF_INET, SOCK_STREAM, 0);
  if(cfd == -1)
    sys_err("socket");

  if(connect(cfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1){
    sys_err("connect");
  }

  char buf[BUFSIZE];
  while(1){
    cout << "Please input your sent to server msg : ";
    cin >> buf;
    write(cfd, buf, strlen(buf));
    read(cfd, buf, sizeof(buf));
    cout << "received server msg : "  << buf << endl;

  }

}

编译运行

g++ -o server server.cpp
g++ -o client client.cpp