用c++编写一次启动Server端和Client端后，首先由Server端发‘1’给Client端，Client端将接收到的数据加1后，发该数据给Server端，Server端再将数据加1后发给Client端，依次类推。直到Server端收到数据20，Client收到19时，两方中断收发。

这是一个简单的Socket编程实例，使用TCP协议实现。以下是Server端的代码：

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<unistd.h>

#define BUF_SIZE 1024
using namespace std;

void error_handling(const char* message);

int main(int argc, char* argv[]){
    int serv_sock, clnt_sock;
    char message[BUF_SIZE];
    int str_len, i;
    
    struct sockaddr_in serv_addr, clnt_addr;
    socklen_t clnt_addr_size;
    
    if(argc!=2){
        cout<<"Usage : "<<argv[0]<<" <port>\n";
        exit(1);
    }
    
    serv_sock=socket(PF_INET, SOCK_STREAM, 0);
    if(serv_sock==-1)
        error_handling("socket() error");
    
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family=AF_INET;
    serv_addr.sin_addr.s_addr=htonl(INADDR_ANY);
    serv_addr.sin_port=htons(atoi(argv[1]));
    
    if(bind(serv_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr))==-1)
        error_handling("bind() error");
    
    if(listen(serv_sock, 5)==-1)
        error_handling("listen() error");
    
    clnt_addr_size=sizeof(clnt_addr);
    clnt_sock=accept(serv_sock, (struct sockaddr*)&clnt_addr, &clnt_addr_size);
    if(clnt_sock==-1)
        error_handling("accept() error");
    
    int data = 1;
    while(data < 21){
        write(clnt_sock, &data, sizeof(data)); // send data to client
        read(clnt_sock, &data, sizeof(data)); // receive data from client
        cout<<"Server received data: "<<data<<endl;
        data++;
    }
    close(clnt_sock);
    close(serv_sock);
    return 0;
}

void error_handling(const char* message){
    cerr<<message<<endl;
    exit(1);
}

以下是Client端的代码：

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<unistd.h>

#define BUF_SIZE 1024
using namespace std;

void error_handling(const char* message);

int main(int argc, char* argv[]){
    int sock;
    char message[BUF_SIZE];
    int str_len;
    int data = 0;
    
    struct sockaddr_in serv_addr;
    
    if(argc!=3){
        cout<<"Usage : "<<argv[0]<<" <IP> <port>\n";
        exit(1);
    }
    
    sock=socket(PF_INET, SOCK_STREAM, 0);
    if(sock==-1)
        error_handling("socket() error");
    
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family=AF_INET;
    serv_addr.sin_addr.s_addr=inet_addr(argv[1]);
    serv_addr.sin_port=htons(atoi(argv[2]));
    
    if(connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr))==-1)
        error_handling("connect() error");
    
    while(data < 20){
        read(sock, &data, sizeof(data)); // receive data from server
        cout<<"Client received data: "<<data<<endl;
        data++;
        write(sock, &data, sizeof(data)); // send data to server
    }
    close(sock);
    return 0;
}

void error_handling(const char* message){
    cerr<<message<<endl;
    exit(1);
}