Client_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
//message structrue
typedef struct
{
    char type;
    char name[32];
    char text[N];
}MSG;
//some variables and structures
int socketfd;
socklen_t addr_len;
pid_t pid;
MSG msg;
struct sockaddr_in client_addr;
//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("uasge: %s ip port\n",argv[0]);
        exit(-1);
    }   
    if((socketfd = socket(PF_INET,SOCK_DGRAM,0)) < 0){
        perror("socket failed");
        exit(-1);
    }
    printf("input name:\n");
    fgets(msg.name,64,stdin);
    msg.name[strlen(msg.name) - 1] = '\0';
    msg.type='L';
    memset(&client_addr,0,sizeof(client_addr));
    client_addr.sin_family = AF_INET;
    client_addr.sin_addr.s_addr = inet_addr(argv[1]);
    client_addr.sin_port = htons(atoi(argv[2]));
    addr_len = sizeof(client_addr);
}
//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(){
    if(sendto(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&client_addr,addr_len) < 0){
        perror("sendto failed3");
        exit(-1);
    }
    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';
            if(strncmp(msg.text,"quit",4) == 0){
                msg.type = 'Q';
                if(sendto(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&client_addr,addr_len) < 0){
                    perror("sendto failed2");
                    exit(-1);
                }
                kill(getppid(),SIGKILL);
                break;  
            }
            else{
                msg.type='B';
                if(sendto(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&client_addr,addr_len) < 0){
                    perror("sendto failed1");
                    exit(-1);
                }   
            }       
        }
        close(socketfd);
    }
    if(pid > 0){
        while(1){
            if(recvfrom(socketfd,&msg,sizeof(msg),0,(struct sockaddr*)&client_addr,&addr_len) < 0){
                perror("recvfrom failed");
                exit(-1);
            }
            switch(msg.type){
                case 'L':
                    printf("%s login\n",msg.name);
                    break;
                case 'B':
                    printf("from %s > %s\n",msg.name,msg.text);
                    break;
                case 'Q':
                    printf("%s quit\n",msg.name);
                    break;
            }
        }
    }
}
//main function
int main(int argc,char *argv[]){    
    init(argc,argv);
    start();
    return 0;
}