Linux FIFO

head.h:

/* head */
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/stat.h>

#define SERVER_FIFO "/tmp/server_fifo"
#define LOGIN    0
#define SEND    1

typedef struct 
{
    int service_type;
    char myfifo[50];

    union {
        struct {
            char username[50];
        }user ;
        struct {
            char name_src[50];
            char name_dst[50];
            char msg[100];
        }msg;
    } choose;
}Message;

typedef struct {
    char name[50];
    char fifo[50];
}User;

server.c

#include "head.h"
#define BUF_SIZE 100

int ser_fifo;
int i;
int fd;
int user_num ;
char buffer[BUF_SIZE];
Message message;
User users[10];

void init(){
    if(access(SERVER_FIFO, F_OK) == -1){
        if(mkfifo(SERVER_FIFO, 0777) == -1){
            perror("init-access-mkfifo");
            exit(1);
        }
    }

    if((ser_fifo = open(SERVER_FIFO, O_RDONLY | O_NONBLOCK)) == -1){
        perror("init-open");
        exit(1);
    }
}


void sendBuffer(){

    if((fd = open(message.myfifo, O_WRONLY | O_NONBLOCK)) == -1){
        perror("sendBuffer-open");
        exit(1);
    }
    if(write(fd, buffer, strlen(buffer)+1) == -1){
        perror("serndBuffer-write");
    }
    close(fd);
}

void login(){
    for (i = 0; i < user_num; ++i)
    {
        if(strcmp(message.choose.user.username, users[i].name) == 0){
            strcpy(buffer,"1,the user has existed");
            break;
        }
    }

    if(i == user_num)
        strcpy(buffer ,"0,login success");
    strcpy(users[user_num].name, message.choose.user.username);
    strcpy(users[user_num++].fifo, message.myfifo);

    sendBuffer();
}

void send(){
    for (i = 0; i < user_num; ++i)
    {
        if(strcmp(message.choose.msg.name_dst, users[i].name) == 0)
            break;
    }
    if(i == user_num)
        strcpy(buffer, "the user is not exist! i=user_num");
    else{
        if((fd = open(users[i].fifo, O_WRONLY | O_NONBLOCK)) == -1){
            perror("send-open");
            exit(1);
        }
        sprintf(buffer, "from %s: %s\n", message.choose.msg.name_src,message.choose.msg.msg);
        if(write(fd, buffer, BUF_SIZE) == -1){
            perror("send-write");
            exit(1);
        }
        close(fd);
        strcpy(buffer, "send success !!");
    }
    sendBuffer();
}

void operation(int type){
    if(type == LOGIN) login();
    else if(type == SEND) send();
}

int main(int argc, char const *argv[])
{
    init();
    while(1){
        if((read(ser_fifo, &message, sizeof(Message) + 50))>0){
            operation(message.service_type);
        }
    }
    return 0;
}

client.c:

#include "head.h"
#define BUF_SIZE 100
char mypipename[100];
char myname[50];
char buffer[BUF_SIZE];
int ser_fifo;
int my_fifo;
Message message;


void init(){
    if(access(SERVER_FIFO, F_OK) == -1){
        perror("init-access");
        exit(1);
    }

    ser_fifo = open(SERVER_FIFO, O_WRONLY);
    if(ser_fifo == -1){
        perror("init-open");
        exit(1);
    }

    sprintf(mypipename, "/tmp/client%d_fifo", getpid());
//    printf("%s",mypipename);
    if(mkfifo(mypipename, 0777) == -1){
        perror("init-mkfifo");
        exit(1);
    }

    my_fifo = open(mypipename, O_RDONLY | O_NONBLOCK);
    if(my_fifo == -1){
        perror("open my fifo");
        exit(1);
    }

    strcpy(message.myfifo, mypipename);
}

void sendMessage(){
    if(write(ser_fifo, &message, sizeof(Message)) == -1){
        perror("sendMessage-write");
        exit(1);
    }
}

recMessage(){
    int res;
    if((res = read(my_fifo, buffer, BUF_SIZE)) == -1){
        perror("recMessage-read");
        exit(1);
    }
    return res;
}

int login(){
    message.service_type = LOGIN;
    printf("username: ");
    scanf("%s", message.choose.user.username);
    sendMessage();
    while(recMessage() == 0) ;
    printf("%s\n", buffer);
    if(buffer[0] == '0'){
        strcpy(myname, message.choose.user.username);
        return 0;
    }
    return -1;
}

void send(){
    message.service_type = SEND;
    printf("message to : ");
    scanf("%s", message.choose.msg.name_dst);
    printf("The message is :\n");
    getchar();
    fgets(message.choose.msg.msg, 100, stdin);
    strcpy(message.choose.msg.name_src, myname);
    sendMessage();
}

int main(int argc, char const *argv[])
{
    init();
    while(login()!= 0);
    int pid;
    if((pid = fork()) == -1){
        perror("main-fork");
        exit(1);
    }

    if(pid == 0){
        while(1){
            if(recMessage() > 0)
                printf("%s\n", buffer);
        }
    }
    else{
        while(1){
            sleep(1);
            send();
        }
    }
    return 0;
}