數(shù)據(jù)報(bào)和流式套接字的工作過程

基本概念
linux操作系統(tǒng)一切皆文件的概念在socket通信過程中體現(xiàn)的十分完整，通過一個(gè)文件描述符來索引一個(gè)socket，創(chuàng)建socket的系統(tǒng)調(diào)用為

相關(guān)參數(shù)的含義可查看manual文檔，其中domain比較特殊，可取下表

#include<stdio.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<netinet/in.h>
int main(){
    int server_fd, client_fd;
    int server_addr_len, client_addr_len;
    struct sockaddr_in server_addr, client_addr;
    server_addr_len = sizeof(server_addr);
    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    server_addr.sin_port = 8000;
    bind(server_fd, (struct sockaddr *)&server_addr, server_addr_len);
    listen(server_fd, 5);
    while(1){
        printf("服務(wù)器等待消息！\n");
        char ch;
        client_addr_len = sizeof(client_addr);
        client_fd = accept(server_fd, 
            (struct sockaddr *) &client_addr, 
            (socklen_t *)&client_addr_len);
        read(client_fd, &ch, 1);
        ch++;
        write(client_fd, &ch, 1);
        close(client_fd);
    }
    return 0;
}

#include<stdio.h>
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<stdlib.h>
#include<string.h>
int main(){
    struct sockaddr_in server_addr;
    int server_addr_len = sizeof(sockaddr_in);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = 8000;
    int socket_fd = socket(AF_INET, SOCK_STREAM, 0);
    char ch = 'A';
    int res;
    
   
    if((res = connect(socket_fd, (sockaddr*) &server_addr, (socklen_t) server_addr_len)) == -1){
        perror("連接目的地址出錯(cuò)！");
        exit(1);
    }
    printf("請(qǐng)輸入字符：\n");
    scanf("%c", &ch);
    
    write(socket_fd, &ch, 1);
    read(socket_fd, &ch, 1);
    printf("%c\n", ch);
    close(socket_fd);
    return 0;
}

//include the header file socket,io,epoll,list,string,unistd,stdlib
#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<fcntl.h>
#include<string.h>
#include<list>
#include<errno.h>
#include<sys/epoll.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>


//namespace
using namespace std;
//client list, C++ stl list<T>
list<int> client_list;
//macro statement server_ip,server_port,epollsize,buf_size,Welcome string,server_string
#define SERVER_IP "127.0.0.1"
#define SERVER_PORT 8888
#define EPOLL_SIZE 500
#define BUF_SIZE 2048
#define WELCOME_STRING "Welcome to join the chat room, your chat ID is: Client# %d"
#define SERVER_STRING "Client id #%d say >> %s"
#define CAUTION "only one client in the chat room"
//set fd in nonblocking io mode, using fnctl
void setNonBlocking(int fd){
    int res = fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | O_NONBLOCK);
    if(res != 0){
        perror("set fd nonblock failed");
        return;
    }
}
//add fd to the epoll,with epoll_ctl
void addFdToEpoll(int epollfd, int sockfd, bool enable_et){
    struct epoll_event event;
    event.events = EPOLLIN;
    if(enable_et){
        event.events = EPOLLIN | EPOLLET;
    }
    event.data.fd = sockfd;
    if(epoll_ctl(epollfd, EPOLL_CTL_ADD, sockfd, &event) != 0){
        perror("add fd to epoll failed");
    };
    setNonBlocking(sockfd);
}
//send broadcast message to the client in clients list, except for which we received the data
void sendBroadcastMessage(int sockfd){
    char buf[BUF_SIZE], message[BUF_SIZE];
    //initialize the space
    bzero(buf, BUF_SIZE);
    bzero(message, BUF_SIZE);

    int rlen = recv(sockfd, buf, BUF_SIZE, 0);
    printf("read data from Client #%d: %s\n", sockfd, buf);
    
    if(rlen == 0){
        close(sockfd);
        client_list.remove(sockfd);
        printf("client #%ld closed, Now, there are %d clients in the chatroom\n",sockfd, client_list.size());
        
    }else{
        if(client_list.size() == 1){
            int slen = send(sockfd, CAUTION, strlen(CAUTION), 0);
            return;
        }
        sprintf(message, SERVER_STRING, sockfd, buf);
        printf("will send:%s\n", message);
        list<int>::iterator iter;
        for( iter = client_list.begin(); iter != client_list.end(); iter++ ){
            puts("sending data...");
            if(*iter != sockfd){
                send(*iter, message, BUF_SIZE, 0);
            }
        }
    }
}

#include "common.h"
int main(){
    //socket address statement
    struct sockaddr_in server_addr;
    //initialize the address
    server_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
    server_addr.sin_port = htons(SERVER_PORT);
    server_addr.sin_family = AF_INET;
    //create server socket
    int listener = socket(AF_INET, SOCK_STREAM, 0);
    //bind the server address
    if(bind(listener, (struct sockaddr*)&server_addr, sizeof(server_addr)) != 0){
        perror("bind failed");
        return 1;
    }
    //listen on the address
    if(listen(listener, 5) != 0){
        perror("listen failed");
        return 2;
    }
    //create epoll
    int epollfd = epoll_create(EPOLL_SIZE);
    if(epollfd < 0){
        perror("create epollfd failed");
        return 3;
    }
    //add server fd to epoll
    addFdToEpoll(epollfd, listener, true);
    //epoll_event array
    static struct epoll_event events[EPOLL_SIZE];
    //main loop
    int clientfd;
    while(1){
        //epoll_wait
        puts("waiting clients...");
        int event_count = epoll_wait(epollfd,events, EPOLL_SIZE, -1);
        printf("epoll event count is %d\n", event_count);
        for(int i = 0; i< event_count; i++){
            clientfd = events[i].data.fd;
             //if fd is serverfd, accept a connection, print information, add new sockfd to epoll
            if(clientfd == listener){
                struct sockaddr_in client_addr;
                socklen_t addrlen = sizeof(struct sockaddr_in);
                int newfd = accept(listener, (struct sockaddr*)&client_addr, &addrlen);
                if(newfd < 0){
                    perror("accept new connections failed");
                    exit(EXIT_FAILURE);
                }
                printf(
                    "new connection from %s:%d, client id #%d\n",
                    inet_ntoa(client_addr.sin_addr),
                    ntohs(client_addr.sin_port),
                    newfd
                );
                addFdToEpoll(epollfd, newfd, true);
                client_list.push_back(newfd);
                printf("welcome message\n");
                char message[BUF_SIZE];
                bzero(message, BUF_SIZE);
                sprintf(message, WELCOME_STRING, newfd);
                send(newfd, message, strlen(message), 0);
            }//if not, sendbroadcast message
            else{
                sendBroadcastMessage(clientfd);
            }
        }
    }
}

#include"common.h"
int main(){
    //server address statement
    struct sockaddr_in server_addr;
    //initilize server address
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    server_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
    //create sock
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if(sock < 0){
        perror("create socket failed");
        return 1;
    }
    if(connect(sock, (struct sockaddr*)&server_addr, sizeof(struct sockaddr_in)) != 0){
        perror("connect server failed");
        return 0;
    }
    int pipefd[2];
    if(pipe(pipefd) != 0){
        perror("create pipe failed");
        return 2;
    }
    int epollfd = epoll_create(EPOLL_SIZE);
    if(epollfd< 0){
        perror("create epollfd failed");
        return 3;
    }
    addFdToEpoll(epollfd, sock, true);
    addFdToEpoll(epollfd, pipefd[0], true);
    pid_t pid = fork();
    if(pid < 0){
        perror("create child process failed");
        return 4;
    }
    int client_running = 1;
    char message[BUF_SIZE];
    char buf[BUF_SIZE];
    struct epoll_event events[2];
    
    if(pid == 0){
        close(pipefd[0]);
        printf("please input your message, and type exit to terminate\n");
        while(client_running){

            //printf("input>");
            bzero(message, BUF_SIZE);
            //bzero(buf, BUF_SIZE);
            fgets(message, BUF_SIZE, stdin);
            if(strncmp(message, "exit", strlen("exit")) == 0){
                client_running = 0;
                close(sock);
                close(pipefd[1]);
                return 0;
                
            }else{
                write(pipefd[1], message, strlen(message));
            }
        }
    }else{
        close(pipefd[1]);
        while(client_running){
            int event_count = epoll_wait(epollfd, events, 2, -1);
            for(int i = 0; i < event_count; i++){
                if(events[i].data.fd == pipefd[0]){
                    bzero(buf, BUF_SIZE);
                    if(read(pipefd[0], buf, BUF_SIZE) == 0){
                        client_running = 0;
                    }else{
                        printf("\nyour input:%s\n", buf);
                        send(sock, buf, strlen(buf) - 1, 0);

                    }
                }else{
                    recv(sock, buf, BUF_SIZE, 0);
                    printf("\nServer message:%s\n", buf);
                }
            }
        }
    }

    close(sock);
    if(pid){
        close(pipefd[0]);
    }else{
        close(pipefd[1]);
    }
    return 0;
}