Linux基础——socket实现简单的群聊程序

首先，我们需要实现数据结构，当有用户连接时，我们将该用户的IP、连接的端口号等保存到一个链表中，

当我们发送消息时，遍历链表，将该消息发送给所有已上线的用户。

当用户下线时，我们将该用户从链表中删除。

服务器实现代码如下:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <sys/time.h>
#define SIZE 1024
typedef struct sockaddr_in SA;
typedef struct tag_msg
{
    int msg_type;
    int msg_len;
    char msg_buf[SIZE];
}MSG,*pMSG;
typedef struct tag
{
    SA addr;
    struct tag *next;
}NODE,*pNODE;
void add_list(pNODE *phead,pNODE p)
{
    p->next = *phead;
    *phead = p;
}
void del_list(pNODE *phead, SA *p)
{
    pNODE pcur,ppre;
    pcur = *phead;
    ppre= NULL;
    while(pcur)
    {
        if(pcur ->addr.sin_port == p->sin_port && pcur->addr.sin_addr.s_addr == p->sin_addr.s_addr)
            break;
        else
        {
            ppre = pcur;
            pcur = pcur->next;
        }
    }
    if(ppre == NULL)
    {
        *phead=pcur ->next;
        free(pcur);
        pcur = NULL;
    }
    else
    {
        ppre->next = pcur ->next;
        free(pcur);
        pcur =NULL;
    }
}
void send_msg(int fd,char *msg,pNODE phead)
{
    while(phead)
    {
        sendto(fd,msg,strlen(msg),0,(struct sockaddr*)&(phead->addr),sizeof(SA));
        phead=phead->next;
    }
}
int main(int argc,char *argv[])
{
    if(argc != 2)
    {
        printf("参数不足!!
");
        exit(1);
    }
    FILE *fp;
    pNODE list=NULL;
    char ip[32];
    int port;
    memset(ip,0,32);
    fp = fopen(argv[1],"r");
    if(fp == NULL)
    {
        perror("fopen");
        exit(1);
    }
    fscanf(fp,"%s%d",ip,&port);
    fclose(fp);
    int fd_server;
    if((fd_server = socket(AF_INET,SOCK_DGRAM,0))==-1)
    {
        perror("socket");
        exit(1);
    }
    SA addr_server;
    memset(&addr_server,0,sizeof(SA));
    addr_server.sin_family = AF_INET;
    addr_server.sin_port = htons(port);
    addr_server.sin_addr.s_addr = inet_addr(ip);
    if(-1 == bind(fd_server,(struct sockaddr *)&addr_server,sizeof(SA)))
    {
        perror("bind");
        close(fd_server);
        exit(1);
    }
    fd_set read_set,ready;
    int sel_ret;
    char buf[1024];
    struct timeval tm;
    MSG my_msg;
    int len = sizeof(SA);
    FD_ZERO(&read_set);
    FD_ZERO(&ready);
    FD_SET(fd_server,&read_set);
    while(1)
    {
        ready = read_set;
        tm.tv_sec=0;
        tm.tv_usec=1000;
        sel_ret = select(fd_server+1,&ready,NULL,NULL,&tm);
        if(sel_ret == 0)
            continue;
        else if(sel_ret == -1)
            continue;
        else if(sel_ret == 1)
        {
            pNODE pnew = (pNODE)calloc(1,sizeof(NODE));
            memset(&my_msg,0,sizeof(MSG));
            recvfrom(fd_server,&my_msg,sizeof(my_msg),0,(struct sockaddr*)&(pnew->addr),&len);
            if(my_msg.msg_type == 1)
            {
                add_list(&list,pnew);
                printf("%s : %d on!!
",inet_ntoa(pnew->addr.sin_addr),ntohs(pnew->addr.sin_port));
            }
            else if(my_msg.msg_type == 3)
            {
                del_list(&list,&(pnew->addr));
                printf("%s : %d off!!
",inet_ntoa(pnew->addr.sin_addr),ntohs(pnew->addr.sin_port));
            }
            else
            {
                memset(buf,0,1024);
                sprintf(buf,"	from %s %d:
%s
",inet_ntoa(pnew->addr.sin_addr),ntohs(pnew->addr.sin_port),my_msg.msg_buf);
                puts(buf);
                send_msg(fd_server,buf,list);
            }
        }
    }
    return 0;
}

客户端实现代码如下:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
typedef struct sockaddr_in SA;
typedef struct tag_msg
{
    int msg_type;
    int msg_len;
    char msg_buf[1024];
}MSG,*pMSG;
int main(int argc,char *argv[])
{
    if(argc != 2)
    {
        perror("参数不足!!
");
        exit(1);
    }
    FILE *fp;
    char ip[32];
    int port;
    memset(ip,0,32);
    fp = fopen(argv[1],"r");
    if(fp == NULL)
    {
        perror("fopen");
        exit(1);
    }
    fscanf(fp,"%s%d",ip,&port);
    fclose(fp);
    int fd_client;
    int len;
    len=sizeof(SA);
    if((fd_client=socket(AF_INET,SOCK_DGRAM,0))==-1)
    {
        perror("socket");
        exit(1);
    }
    SA addr_client;
    memset(&addr_client,0,sizeof(SA));
    addr_client.sin_family = AF_INET;
    addr_client.sin_port = htons(port);
    addr_client.sin_addr.s_addr=inet_addr(ip);
    MSG my_msg={1,2,"on"};
    sendto(fd_client,&my_msg,8+my_msg.msg_len,0,(struct sockaddr*)&addr_client,sizeof(SA));
    if(fork() == 0)
    {
        if(fork() == 0)
        {
            char info[1024];
            while(memset(info,0,1024),recvfrom(fd_client,info,1024,0,NULL,NULL)>0)
                write(1,info,strlen(info));
            exit(0);
        }
        close(fd_client);
        exit(0);
    }
    wait(NULL);
    while(memset(&my_msg,0,sizeof(MSG)),fgets(my_msg.msg_buf,1024,stdin)!=NULL)
    {
        my_msg.msg_type =2;
        my_msg.msg_len = strlen(my_msg.msg_buf);
        sendto(fd_client,&my_msg,8+my_msg.msg_len,0,(struct sockaddr*)&addr_client,sizeof(SA));
    }
    my_msg.msg_type = 3;
    my_msg.msg_len=0;
    sendto(fd_client,&my_msg,8+my_msg.msg_len,0,(struct sockaddr*)&addr_client,sizeof(SA));
    close(fd_client);
    return 0;
}

我相应的IP、port文件如下:

192.168.0.124
10000