Group chat room based on UDP

1.UDP The function of group chat

There are new users logging in , Other online users can receive login information

User group chat , Other online users can receive group chat information

Some users quit , Other online users can receive the exit message

The server can send system information

2 Write the process of the project

Draw flow chart

Write the framework according to the flow chart

One function, one function

3 flow chart

 4 Code implementation

4.1 The header file

#ifndef __MYHEAD_H__
#define __MYHEAD_H__

#include <head.h>
#define N 512
// The structure of chat operation 
typedef struct _MSG{
    char ch;// be used for 'l' Chat ,'q' sign out ,' Sign in d'
    char name[128];// Save your name 
    char text[N];// Save chat content 
}msg_t;
// The structure used to store each user's information 
typedef struct _Jilu{
    struct sockaddr_in addr;
    struct _Jilu *next;
}jilu_t;


int create_head(jilu_t **head);
int input_addr(jilu_t *head,msg_t msg,int sockfd,struct sockaddr_in clientaddr,socklen_t clientaddr_len);
int wx_addr(jilu_t *head,msg_t msg,int sockfd,struct sockaddr_in clientaddr,socklen_t clientaddr_len);
int tuichu_addr(jilu_t *head,msg_t msg,int sockfd,struct sockaddr_in clientaddr,socklen_t clientaddr_len);
#endif

4.2 function

#include "myhead.h"

// Create a single chain header 
int create_head(jilu_t **head)
{   
    if(head==NULL){
        printf(" Transmission error , Please check \n");
        return -1;
    }

    (*head)=(jilu_t *)malloc(sizeof(jilu_t));
    (*head)->next=NULL;

    return 0;

}

// Record the information of the logged in user 
int input_addr(jilu_t *head,msg_t msg,int sockfd,struct sockaddr_in clientaddr,socklen_t clientaddr_len)
{
    if(head==NULL){
        printf(" Transmission error , Please check \n");
        return -1;
    }

    // Send the login information of this user to everyone 
    snprintf(msg.text,sizeof(msg.text),"[%s]%s",msg.name," Log on to the ");
    // This is used to record the address of the header 
    jilu_t *jilu_head=head;

    while(jilu_head->next!=NULL){
        jilu_head=jilu_head->next;
        if(sendto(sockfd,&msg,sizeof(msg),0,(struct sockaddr*)&jilu_head->addr,clientaddr_len)==-1){
            ERRLOG(" Failed to send the user login information to everyone ");
        }
    }
    // Create a new node , And put the new user information into the new order list 
    jilu_t *temp=NULL;
    create_head(&temp);
    temp->addr=clientaddr;

    // Insert the user information into the linked list with header insertion 
    temp->next=head->next;
    head->next=temp;

    return 0;
}
 
int wx_addr(jilu_t *head,msg_t msg,int sockfd,struct sockaddr_in clientaddr,socklen_t clientaddr_len)
{
    
    if(head==NULL){
        printf(" Transmission error , Please check \n");
        return -1;
    }

    // Send the received message to everyone except yourself 
    jilu_t *jilu_head=head;
    while(jilu_head->next!=NULL){
        jilu_head=jilu_head->next;
        if(0!=memcmp(&(jilu_head->addr),&clientaddr,sizeof(clientaddr))){     
            if(sendto(sockfd,&msg,sizeof(msg),0,(struct sockaddr*)&jilu_head->addr,clientaddr_len)==-1){
                ERRLOG(" Failed to send the chat content to everyone ");
            }
        }
    }

    return 0;
}
int tuichu_addr(jilu_t *head,msg_t msg,int sockfd,struct sockaddr_in clientaddr,socklen_t clientaddr_len)
{
    if(head==NULL){
        printf(" Transmission error , Please check \n");
        return -1;
    }

    snprintf(msg.text,sizeof(msg.text),"%s%s",msg.name," Log out ");

    jilu_t *jilu_head=head;
    jilu_t *pdel=NULL;
    
    while(jilu_head->next!=NULL){
        
        if(0==memcmp(&(jilu_head->next->addr),&clientaddr,sizeof(clientaddr))){
            pdel=jilu_head->next;
            jilu_head->next=pdel->next;
            free(pdel);
            pdel=NULL;
        }else{
            jilu_head=jilu_head->next;
            if(sendto(sockfd,&msg,sizeof(msg),0,(struct sockaddr*)&jilu_head->addr,clientaddr_len)==-1){
                ERRLOG(" Tell everyone about this exit message and fail ");
            }
        }
    }

   
    return 0;
}

4.3 The server

#include "myhead.h"

int main(int argc, char const *argv[])
{
    int sockfd=0;
    pid_t pid=0;
    msg_t msg;// Used for various operations 
    msg_t faso;// Used to send system messages 

    if((sockfd=socket(AF_INET,SOCK_DGRAM,0))==-1){
        ERRLOG(" Failed to create server socket ");
    }

    // Put the network information structure into the server 
    struct sockaddr_in serveraddr;
    memset(&serveraddr,0,sizeof(serveraddr));
    serveraddr.sin_family=AF_INET;
    serveraddr.sin_port=htons(atoi(argv[2]));
    serveraddr.sin_addr.s_addr=inet_addr(argv[1]);
    socklen_t serveraddr_len=sizeof(serveraddr);

    // Bind the socket to the network information structure 
    if(bind(sockfd,(struct sockaddr*)&serveraddr,serveraddr_len)==-1){
        ERRLOG(" Binding socket to network information structure failed ");
    }

    // Create a new network information structure to store client information 
    struct sockaddr_in clientaddr;
    clientaddr.sin_family=AF_INET;
    socklen_t clientaddr_len=sizeof(clientaddr);
    
    // Create a process 
    pid=fork();
    if(pid==-1){
        ERRLOG(" Server creation process failed ");
    }else if(pid==0){
        // Create a single list to save the network information structure 
        jilu_t *head;
        create_head(&head);
        memset(&msg,0,sizeof(msg));
        while(1){
            if(recvfrom(sockfd,&msg,sizeof(msg),0,(struct sockaddr*)&clientaddr,&clientaddr_len)==-1){
                ERRLOG(" Failed to accept the information from the client ");
            }          
             switch(msg.ch){
                case 'd':// login information 
                    input_addr(head,msg,sockfd,clientaddr,clientaddr_len);
                    //head->next=NULL; // This is for testing                   
                    break;
                case 'l':// Chat messages 
                    wx_addr(head,msg,sockfd,clientaddr,clientaddr_len);
                    break;
                case 'q':// Exit message 
                    tuichu_addr(head,msg,sockfd,clientaddr,clientaddr_len);
                    break;
            }
        }
    }else{
        while(1){
            // Send system messages 
            memset(&faso,0,sizeof(faso));
            fgets(faso.text,sizeof(faso.text),stdin);
            faso.text[strlen(faso.text)-1]='\0';
            faso.ch='l';
            sprintf(faso.name,"%s"," System message ");

            if(sendto(sockfd,&faso,sizeof(faso),0,(struct sockaddr*)&serveraddr,serveraddr_len)==-1){
                ERRLOG(" Sending system message failed ");
            }
        }
    }
    return 0;
}

4.4 client

#include "myhead.h"


int main(int argc, char const *argv[])
{

    // Judge whether the input is correct 
    if(argc!=3){
        printf(" Input format error ,./a.out ip port\n");
        exit(EXIT_SUCCESS);
    }

    int sockfd=0;
    pid_t pid=0;
    msg_t msg;// Create and send user information 
    

    if((sockfd=socket(AF_INET,SOCK_DGRAM,0))==-1){
        ERRLOG(" Failed to create client socket ");
    }

    // Bind the client network information structure 
    struct sockaddr_in clientaddr;
    memset(&clientaddr,0,sizeof(clientaddr));
    clientaddr.sin_family=AF_INET;
    clientaddr.sin_port=htons(atoi(argv[2]));
    clientaddr.sin_addr.s_addr=inet_addr(argv[1]);
    socklen_t clientaddr_len=sizeof(clientaddr);

    // Enter the user's name to log in 
    msg.ch='d';
    printf(" Please enter the name you use to sign in ");
    fgets(msg.name,sizeof(msg.name),stdin);
    msg.name[strlen(msg.name)-1]='\0';

    // Send the operation that the user has logged in to the server 
    if(sendto(sockfd,&msg,sizeof(msg),0,(struct sockaddr*)&clientaddr,clientaddr_len)==-1){
        ERRLOG(" The login information sent by the client to the server failed ");
    }
    
    // Create a process , Subprocesses are used to accept , The parent process is used to send 
    pid=fork();
    if(pid==-1){
        ERRLOG(" Client creation process failed ");
    }else if(pid==0){
        // Used to receive messages from the server 
        while(1){
            memset(&msg,0,sizeof(msg));
            if(recvfrom(sockfd,&msg,sizeof(msg),0,NULL,NULL)==-1){
                ERRLOG(" The message sent by the receiving server is wrong ");
            }

            printf("[%s]>>(%s)\n",msg.name,msg.text);
        }
    }else{
        // Write the content to be chatted 
        while(1){
            memset(msg.text,0,sizeof(msg.text));
            fgets(msg.text,sizeof(msg.text),stdin);
            msg.text[strlen(msg.text)-1]='\0';

            if(strncmp("quit",msg.text,5)==0){
                msg.ch='q';
            }else{
                msg.ch='l';
            }
            
            // Send the written content to the server 
            if(sendto(sockfd,&msg,sizeof(msg),0,(struct sockaddr*)&clientaddr,clientaddr_len)==-1){
                ERRLOG(" Failed to send chat content to the server ");
            }

            // When the stop is recognized , Close the process 
            if(strncmp("quit",msg.text,5)==0){
                kill(pid,SIGKILL);
                close(sockfd);
                exit(EXIT_SUCCESS);
            }
        }
    }   

    return 0;
}