단순 순환 서버 구현

#include
#include
#include
#include
#include
#include
#include
#include 
#include

#define MAXLINE 4096

int main(int argc, char** argv)
{
    int    sockfd, n,rec_len;
    char    recvline[4096], sendline[4096];
    char    buf[MAXLINE];
    struct sockaddr_in    servaddr;
    // 
    if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        printf("create socket error: %s(errno: %d)
", strerror(errno),errno);
        exit(0);
    }
    // servaddr ， 0
    memset(&servaddr, 0, sizeof(servaddr));
    // 
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    servaddr.sin_port = htons(8000);
//    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);//IP INADDR_ANY, IP 。
    // 
    if( connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0){
        printf("connect error: %s(errno: %d)
",strerror(errno),errno);
        exit(0);
    }
    printf("send msg to server: 
");
    fgets(sendline, 4096, stdin);
    // 
    if( send(sockfd, sendline, strlen(sendline), 0) < 0)
    {
        printf("send msg error: %s(errno: %d)
", strerror(errno), errno);
        exit(0);
    }
    // 
    if((rec_len = recv(sockfd, buf, MAXLINE,0)) == -1) {
        perror("recv error");
        exit(1);
    }
    buf[rec_len]  = '\0';
    printf("Received : %s ",buf);
    // 
    close(sockfd);  
    exit(0);  
}

#include
#include
#include
#include
#include
#include
#include
#include 
#include 
#define DEFAULT_PORT 8000
#define MAXLINE 4096
int main(int argc, char** argv)
{
    int    socket_fd, connect_fd;
    struct sockaddr_in     servaddr, remotaddr;
    char    buff[4096];
    int     n;
    // Socket
    if( (socket_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1 ){
        printf("create socket error: %s(errno: %d)
",strerror(errno),errno);
        exit(0);
    }
    // 
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);//IP INADDR_ANY, IP 。
    servaddr.sin_port = htons(DEFAULT_PORT);// DEFAULT_PORT
    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    
    // 
    if( bind(socket_fd, (struct sockaddr*)&servaddr, sizeof(servaddr)) == -1){
        printf("bind socket error: %s(errno: %d)
",strerror(errno),errno);
        exit(0);
    }
    // 
    if( listen(socket_fd, 10) == -1){
        printf("listen socket error: %s(errno: %d)
",strerror(errno),errno);
        exit(0);
    }
    printf("==========waiting for client's request==========
");
    while(1){
        // ， CPU 。sizeof(struct sockaddr)
        socklen_t addrsize = sizeof(struct sockaddr);
        if((connect_fd = accept(socket_fd, (struct sockaddr*)&remotaddr, &addrsize)) == -1){
            if (errno == EINTR)
                continue;
            else
                printf("accept socket error: %s(errno: %d)
",strerror(errno),errno);
                continue;
        }
        printf("accept from ip: %s
", inet_ntoa(remotaddr.sin_addr));
        // 
        n = recv(connect_fd, buff, MAXLINE, 0);
        buff[n] = '\0';
        // 
        if(!fork()){ /* */
            if(send(connect_fd, buff, sizeof(buff),0) == -1)
                perror("send error
");
            close(connect_fd);
            exit(0);
        }
        
        printf("recv msg from client: %s
", buff);
        close(connect_fd);  
    }  
    close(socket_fd);  
}