#include <asm-generic/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>

int main(){
    int socketfd, clientfd;
    struct sockaddr_in address, client_address;
    int addrlen;
    char buffer[1024] = {0};

    // 可以使用strace -p pid 来监视该进程的系统调用，观察阻塞的位置
    printf("current pid=%d\n", getpid());

    socketfd = socket(AF_INET,SOCK_STREAM,0);
    if(socketfd == 0){
        perror("socket created failed\n");
        exit(-1);
    }

    // 开始进行一些设置，防止反复重启测试的时候不能立即使用同一个端口
    // optname : 
    // SO_REUSEADDR 使用同一个端口，绑定不同的ip地址
    // SO_REUSEPORT 多个进程或者线程 监听同一个ip和port
    int optval = 1;
    if(setsockopt(socketfd, SOL_SOCKET, SO_REUSEPORT, (const void*)&optval, sizeof(optval))){
        perror("setsocketopt failed\n");
        exit(-1);
    }

    // 1. 协议簇(ipv4, ipv6) 2. ip 3. port
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(8989);
    if(bind(socketfd, (const struct sockaddr*)&address,sizeof(address)) < 0){
        perror("socket created failed\n");
        exit(-1);
    }

    // backlog = 511， 意味着当没有被accept可以堆积多少个fd
    if(listen(socketfd, 511) < 0){
        perror("listen error");
        exit(-1);
    }
    printf("start listening\n");
    while(1){
        clientfd = accept(socketfd, (struct sockaddr *)&client_address, (socklen_t*)&addrlen);
        if(clientfd < 0){
            perror("accept failed\n");
            exit(-1);
        }
        printf("accept client=%d\n", clientfd);
        memset(buffer, 0, 1024);
        int n = read(clientfd, buffer, 1024);
        if(n == 0){
            printf("client:%d close the socket\n",clientfd);
            close(clientfd);
            continue;
        }
        printf("read from client : %s\n", buffer);
        write(clientfd, buffer, n);
        close(clientfd);
    }

    return 0;
}

#include <stdio.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <arpa/inet.h>

int main()
{
    int clientfd;
    struct sockaddr_in address;
    char* hello = "hello from client";
    char buffer[1024] = {0};

    clientfd = socket(AF_INET, SOCK_STREAM, 0);
    if(clientfd < 0){
        perror("clientfd create failed\n");
        exit(-1);
    }

    address.sin_family = AF_INET;
    address.sin_addr.s_addr = inet_addr("127.0.0.1");
    address.sin_port = htons(8989);

    if(connect(clientfd, (const struct sockaddr*)&address, sizeof(address)) < 0)
    {
        perror("connect error\n");
        exit(-1);
    }

    write(clientfd, hello, strlen(hello));
    int n = read(clientfd, buffer, 1024);
    printf("receive from server : %s\n", buffer);
    close(clientfd);
    return 0;
}