基于UDP协议我的聊天室！！！

服务器功能：

1、显示目前上线与下线情况；

2、广播通知用户登录、退出情况；

3、接受客户消息转发给所有客户端；

客户端功能：

1、接受服务器信息并显示；

2、发送消息给服务器端（指向群用户）；

CODE：

服务器端：

#include "server.h" //可能用到的头文件；

#include "server.h"

int main()
{
    int sockfd;
    struct sockaddr_in serveraddr, clientaddr;
    struct sockaddr_in addrbuf[20];
    char buf[MAXBUF];
    int length;

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    memset(&serveraddr, 0, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    serveraddr.sin_port = htons(8000);
    serveraddr.sin_addr.s_addr = inet_addr("192.168.0.104");

    bind(sockfd, (SA *)&serveraddr, sizeof(serveraddr));

    length = sizeof(clientaddr);

    int i = 0;
    int j;
    char buf_addr[50];
    char bufport[10];

    while(1)
    {
        memset(buf, '\0', sizeof(buf));
        recvfrom(sockfd, buf, sizeof(buf), 0, (SA *)&clientaddr, &length);

        if(strcmp("IN", buf) == 0)
        {
            printf("%s:%d is on line\n", inet_ntoa(clientaddr.sin_addr),\
                    ntohs(clientaddr.sin_port));

            addrbuf[i] = clientaddr;
            i ++;

            sprintf(buf_addr, "%s",inet_ntoa(clientaddr.sin_addr));
            sprintf(bufport, ":%d is on line ...", ntohs(clientaddr.sin_port));
            strcat(buf_addr, bufport);

            for(j = 0; j < i; j ++)
            {
                sendto(sockfd, buf_addr, sizeof(buf_addr), 0, (SA *)&(addrbuf[j]), sizeof(addrbuf[j]));
            }

        }
        else if(strcmp("quit",buf) == 0)
        {
            printf("%s:%d is off line\n", inet_ntoa(clientaddr.sin_addr),\
                    ntohs(clientaddr.sin_port));
            j = 0;
            while(addrbuf[j].sin_addr.s_addr != clientaddr.sin_addr.s_addr ||
                    addrbuf[j].sin_port != clientaddr.sin_port)
            {
                j ++;
            }
            //j --;

            int k;
            for(k = j; k < i - 1; k ++)
                addrbuf[k] = addrbuf[k + 1];
            i --;


            sprintf(buf_addr, "%s",inet_ntoa(clientaddr.sin_addr));
            sprintf(bufport, ":%d is off line ...", ntohs(clientaddr.sin_port));
            strcat(buf_addr, bufport);

            for(j = 0; j < i; j ++)
            {
                sendto(sockfd, buf_addr, sizeof(buf_addr), 0, (SA *)&(addrbuf[j]), sizeof(addrbuf[j]));
            }
        }
        else
        {
            char bufport[MAXBUF + 10];
            sprintf(bufport, "%d say :",ntohs(clientaddr.sin_port));
            strcat(bufport,buf);

            for(j = 0; j < i; j ++)
            {
                sendto(sockfd, bufport, sizeof(bufport), 0, (SA *)&(addrbuf[j]), sizeof(addrbuf[j]));
            }
            /*
            for(j = 0; j < i; j ++)
                printf("%s:%d say: %s\n", inet_ntoa(addrbuf[j].sin_addr),\
                        ntohs(addrbuf[j].sin_port),buf);
            */

        }


    }

    return 0;
}

客户端：

#include "client.h"
#include <signal.h>

void exit_fc()
{
    exit(0);
    return ;
}

int main()
{
    int sockfd,length;
    struct sockaddr_in serveraddr;
    char buf[MAXBUF];
    pid_t pid;

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    memset(&serveraddr, 0, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    serveraddr.sin_port = htons(8000);
    serveraddr.sin_addr.s_addr = inet_addr("192.168.0.104");

    printf("*******************chat room******************\n");
    printf("==============================================\n");

    memset(buf, '\0', sizeof(buf));
    buf[0] = 'I';
    buf[1] = 'N';
    buf[2] = '\0';
    sendto(sockfd, buf, sizeof(buf), 0, (SA *)&serveraddr, sizeof(serveraddr));

    length = sizeof(serveraddr);
    sleep(1);
    while(1)
    {
        if((pid = fork())==0)
        {
            while(1)
            {
                memset(buf, '\0', sizeof(buf));
                //printf("Send:");
                fgets(buf, MAXBUF, stdin);
                buf[strlen(buf) - 1] = '\0';
                sendto(sockfd, buf, sizeof(buf), 0, (SA *)&serveraddr, sizeof(serveraddr));

                if(strcmp("quit", buf) == 0)
                {
                    kill(getppid(), SIGUSR1);
                    break;
                }
            }

            exit(0);
        }
        else if(pid > 0)
        {
            signal(SIGUSR1, exit_fc);
            while(1)
            {
                memset(buf,'\0', sizeof(buf));
                recvfrom(sockfd, buf, sizeof(buf), 0, (SA *)&serveraddr, &length);
                printf("%s\n",buf);
            }
            wait(NULL);
            exit(0);
            break;
        }
        else
        {
            perror("fail to connect!\n");
            break;
        }
    }

    return 0;
}