Server_UDP.c

ChatRoom

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <signal.h>
#define N 128
#define L 1
#define B 2
#define Q 3
//message structrue
typedef struct{
    char type;
    char name[32];
    char text[N];
}MSG;
//linklist to save socket addresses
typedef struct node{
    struct sockaddr_in addr;
    struct node *next;
}listnode,*linklist;
//some variables and structures
int socketfd;
socklen_t addr_len;
pid_t pid;
MSG msg;
struct sockaddr_in server_addr,client_addr;
//create the head of linklist
linklist linklist_create(){
    linklist H;
    H = (linklist)malloc(sizeof(listnode));     //apply room from system
    memset(H,0,sizeof(listnode));               //set value for the room that H point
    H -> next = NULL;                           //set "next" as dangling pointer
    return H;
}
//insert data into linklist
void insert_data(linklist H,struct sockaddr_in client_addr){
    linklist p = NULL;
    p = (linklist)malloc(sizeof(listnode));
    p -> addr = client_addr;
    p -> next = H -> next;
    H -> next = p;
    return ;
}
//the process for users to login
void process_login(int socketfd,linklist H,MSG msg,struct sockaddr_in client_addr){
    insert_data(H,client_addr);
    linklist h1 = H;
    while(h1 -> next != NULL){
        h1 = h1 -> next;
        if(memcmp(&client_addr,&h1 -> addr,sizeof(client_addr)) != 0){
            if(sendto(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&(h1 -> addr),sizeof(h1 -> addr)) < 0){
                perror("sendto failed4");
                exit(-1);
            }
        }
    }
    return ;
}
//the process broadcasting messages to each user
void process_broadcast(int socketfd,linklist H,MSG msg,struct sockaddr_in client_addr){
    linklist h1 = H;
    while(h1 -> next != NULL){
        h1 = h1 -> next;
        if(memcmp(&client_addr,&h1->addr,sizeof(client_addr)) != 0){
            if(sendto(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&(h1 -> addr),sizeof(h1 -> addr)) < 0){
                perror("sendto failed3");
                exit(-1);
            }
        }
    }
    return ;
}
//the process run if a user quits
void process_quit(int socketfd,linklist H,MSG msg,struct sockaddr_in client_addr){
    linklist p = H;
    linklist q;
    while(p -> next){
        if(memcmp(&client_addr,&p -> next -> addr,sizeof(client_addr)) == 0){
            q = p -> next;
            p -> next = q -> next;
            free(q);
            q = NULL;
        }
        else{
            if(sendto(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&p->next->addr,sizeof(p->next->addr)) < 0){
                perror("sendto failed2");
                exit(-1);
            }
            p = p -> next;
        }
    }
    return ;
}
//fork function runs once will return two result,the one is 0(means parent process),the other is the ip of the child process
void start(){
    linklist H = linklist_create(); 
    if ((pid = fork()) == -1){
        perror("fork failed");
        exit(-1);
    }
    if (pid == 0){
        while(1){
            fgets(msg.text,N,stdin);
            msg.text[strlen(msg.text)-1] = '\0';
            strcpy(msg.name,"server");
            msg.type = 'B';
            if (sendto(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&server_addr,sizeof(server_addr)) < 0){
                perror("sendto failed1");
                close(socketfd);
                exit(-1);
            }
        }
    }
    if(pid > 0){
        while(1){
            if (recvfrom(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&client_addr,&addr_len) < 0){
                perror("recvfrom");
                close(socketfd);
                exit(-1);
            }
            switch(msg.type){
                case 'L':
                    process_login(socketfd,H,msg,client_addr);
                    break;
                case 'B':
                    process_broadcast(socketfd,H,msg,client_addr);
                    break;
                case 'Q':
                    process_quit(socketfd,H,msg,client_addr);
                    break;
            }
        }
    }
}
//the initialize function,'argc' means the number of the arrays 'argv','argv[0]' means the path of this file
//'argv[1]' and 'argv[2]' mean the two parameters you pass in,the first one is ip,the second one is port
void init(int argc,char *argv[]){
    if (argc < 3){
        printf("usage: %s ip port\n",argv[0]);
        exit(-1);
    }
    memset(&server_addr,0,sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(argv[1]);
    server_addr.sin_port = htons(atoi(argv[2]));
    if((socketfd = socket(PF_INET,SOCK_DGRAM,0)) < 0){
        perror("socket failed");
        exit(-1);
    }
    if(bind(socketfd,(struct sockaddr*)&server_addr,sizeof(server_addr)) < 0){
        perror("bind failed");
        exit(-1);
    }
    addr_len = sizeof(client_addr);
}
//main function
int main(int argc,char *argv[]){
    init(argc,argv);
    start();
    return 0;
}