#ifndef _CLIENT_LINK_LIST_H_
#define _CLIENT_LINK_LIST_H_

#include <WinSock2.h>

#include <stdio.h>

//客户端信息结构体
typedef struct _Client
{
 SOCKET sClient;   //客户端套接字
 char buf[128];   //数据缓冲区
 char userName[16];  //客户端用户名
 char IP[20];   //客户端IP
 unsigned short Port; //客户端端口
 UINT_PTR flag;   //标记客户端，用来区分不同的客户端
 char ChatName[16];  //指定要和哪个客户端聊天
 _Client* next;   //指向下一个结点
}Client, *pClient;

/* * function 初始化链表 * return 无返回值 */
void Init();

/* * function 获取头节点 * return 返回头节点 */
pClient GetHeadNode();

/* * function 添加一个客户端 * param client表示一个客户端对象 * return 无返回值 */
void AddClient(pClient client);

/* * function 删除一个客户端 * param flag标识一个客户端对象 * return 返回true表示删除成功，false表示失败 */
bool RemoveClient(UINT_PTR flag);

/* * function 根据name查找指定客户端 * param name是指定客户端的用户名 * return 返回一个client表示查找成功，返回INVALID_SOCKET表示无此用户 */
SOCKET FindClient(char* name);

/* * function 根据SOCKET查找指定客户端 * param client是指定客户端的套接字 * return 返回一个pClient表示查找成功，返回NULL表示无此用户 */
pClient FindClient(SOCKET client);

/* * function 计算客户端连接数 * param client表示一个客户端对象 * return 返回连接数 */
int CountCon();

/* * function 清空链表 * return 无返回值 */
void ClearClient();

/* * function 检查连接状态并关闭一个连接 * return 返回值 */
void CheckConnection();

/* * function 指定发送给哪个客户端 * param FromName，发信人 * param ToName, 收信人 * param data, 发送的消息 */
void SendData(char* FromName, char* ToName, char* data);


#endif //_CLIENT_LINK_LIST_H_

#include "ClientLinkList.h"

pClient head = (pClient)malloc(sizeof(_Client)); //创建一个头结点

/* * function 初始化链表 * return 无返回值 */
void Init()
{
 head->next = NULL;
}

/* * function 获取头节点 * return 返回头节点 */
pClient GetHeadNode()
{
 return head;
}

/* * function 添加一个客户端 * param client表示一个客户端对象 * return 无返回值 */
void AddClient(pClient client)
{
 client->next = head->next; //比如：head->1->2,然后添加一个3进来后是
 head->next = client;  //3->1->2,head->3->1->2
}

/* * function 删除一个客户端 * param flag标识一个客户端对象 * return 返回true表示删除成功，false表示失败 */
bool RemoveClient(UINT_PTR flag)
{
 //从头遍历，一个个比较
 pClient pCur = head->next;//pCur指向第一个结点
 pClient pPre = head;  //pPre指向head 
 while (pCur)
 {
  // head->1->2->3->4,要删除2，则直接让1->3
  if (pCur->flag == flag)
  {
   pPre->next = pCur->next;
   closesocket(pCur->sClient); //关闭套接字
   free(pCur); //释放该结点
   return true;
  }
  pPre = pCur;
  pCur = pCur->next;
 }
 return false;
}

/* * function 查找指定客户端 * param name是指定客户端的用户名 * return 返回socket表示查找成功，返回INVALID_SOCKET表示无此用户 */
SOCKET FindClient(char* name)
{
 //从头遍历，一个个比较
 pClient pCur = head;
 while (pCur = pCur->next)
 {
  if (strcmp(pCur->userName, name) == 0)
   return pCur->sClient;
 }
 return INVALID_SOCKET;
}

/* * function 根据SOCKET查找指定客户端 * param client是指定客户端的套接字 * return 返回一个pClient表示查找成功，返回NULL表示无此用户 */
pClient FindClient(SOCKET client)
{
 //从头遍历，一个个比较
 pClient pCur = head;
 while (pCur = pCur->next)
 {
  if (pCur->sClient == client)
   return pCur;
 }
 return NULL;
}

/* * function 计算客户端连接数 * param client表示一个客户端对象 * return 返回连接数 */
int CountCon()
{
 int iCount = 0;
 pClient pCur = head;
 while (pCur = pCur->next)
  iCount++;
 return iCount;
}

/* * function 清空链表 * return 无返回值 */
void ClearClient()
{
 pClient pCur = head->next;
 pClient pPre = head;
 while (pCur)
 {
  //head->1->2->3->4,先删除1，head->2,然后free 1
  pClient p = pCur;
  pPre->next = p->next;
  free(p);
  pCur = pPre->next;
 }
}

/* * function 检查连接状态并关闭一个连接 * return 返回值 */
void CheckConnection()
{
 pClient pclient = GetHeadNode();
 while (pclient = pclient->next)
 {
  if (send(pclient->sClient, "", sizeof(""), 0) == SOCKET_ERROR)
  {
   if (pclient->sClient != 0)
   {
    printf("Disconnect from IP: %s,UserName: %s\n", pclient->IP, pclient->userName);
    char error[128] = { 0 }; //发送下线消息给发消息的人
    sprintf(error, "The %s was downline.\n", pclient->userName);
    send(FindClient(pclient->ChatName), error, sizeof(error), 0);
    closesocket(pclient->sClient); //这里简单的判断：若发送消息失败，则认为连接中断(其原因有多种)，关闭该套接字
    RemoveClient(pclient->flag);
    break;
   }
  }
 }
}

/* * function 指定发送给哪个客户端 * param FromName，发信人 * param ToName, 收信人 * param data, 发送的消息 */
void SendData(char* FromName, char* ToName, char* data)
{
 SOCKET client = FindClient(ToName); //查找是否有此用户
 char error[128] = { 0 };
 int ret = 0;
 if (client != INVALID_SOCKET && strlen(data) != 0)
 {
  char buf[128] = { 0 };
  sprintf(buf, "%s: %s", FromName, data); //添加发送消息的用户名
  ret = send(client, buf, sizeof(buf), 0);
 }
 else//发送错误消息给发消息的人
 {
  if(client == INVALID_SOCKET)
   sprintf(error, "The %s was downline.\n", ToName);
  else
   sprintf(error, "Send to %s message not allow empty, Please try again!\n", ToName);
  send(FindClient(FromName), error, sizeof(error), 0);
 }
 if (ret == SOCKET_ERROR)//发送下线消息给发消息的人
 {
  sprintf(error, "The %s was downline.\n", ToName);
  send(FindClient(FromName), error, sizeof(error), 0);
 }

}

/*

#include <WinSock2.h>
#include <process.h>
#include <stdlib.h>
#include "ClientLinkList.h"
#pragma comment(lib,"ws2_32.lib")


SOCKET g_ServerSocket = INVALID_SOCKET;  //服务端套接字
SOCKADDR_IN g_ClientAddr = { 0 };   //客户端地址
int g_iClientAddrLen = sizeof(g_ClientAddr);

typedef struct _Send
{
 char FromName[16];
 char ToName[16];
 char data[128];
}Send,*pSend;




//发送数据线程
unsigned __stdcall ThreadSend(void* param)
{
 pSend psend = (pSend)param; //转换为Send类型
 SendData(psend->FromName, psend->ToName, psend->data); //发送数据
 return 0;
}


//接受数据
unsigned __stdcall ThreadRecv(void* param)
{
 int ret = 0;
 while (1)
 {
  pClient pclient = (pClient)param;
  if (!pclient)
   return 1;
  ret = recv(pclient->sClient, pclient->buf, sizeof(pclient->buf), 0);
  if (ret == SOCKET_ERROR)
   return 1;
  if (pclient->buf[0] == '#' && pclient->buf[1] != '#') //#表示用户要指定另一个用户进行聊天
  {
   SOCKET socket = FindClient(&pclient->buf[1]); //验证一下客户是否存在
   if (socket != INVALID_SOCKET)
   {
    pClient c = (pClient)malloc(sizeof(_Client));
    c = FindClient(socket);      //只要改变ChatName,发送消息的时候就会自动发给指定的用户了
    memset(pclient->ChatName, 0, sizeof(pclient->ChatName)); 
    memcpy(pclient->ChatName , c->userName,sizeof(pclient->ChatName));
   }
   else 
    send(pclient->sClient, "The user have not online or not exits.",64,0);
   continue;
  }

  pSend psend = (pSend)malloc(sizeof(_Send));
  //把发送人的用户名和接收消息的用户和消息赋值给结构体，然后当作参数传进发送消息进程中
  memcpy(psend->FromName, pclient->userName, sizeof(psend->FromName));
  memcpy(psend->ToName, pclient->ChatName, sizeof(psend->ToName));
  memcpy(psend->data, pclient->buf, sizeof(psend->data));
  _beginthreadex(NULL, 0, ThreadSend, psend, 0, NULL);
  Sleep(200);
 }

 return 0;
}

//开启接收消息线程
void StartRecv()
{
 pClient pclient = GetHeadNode();
 while (pclient = pclient->next)
  _beginthreadex(NULL, 0, ThreadRecv, pclient, 0, NULL);
}

//管理连接
unsigned __stdcall ThreadManager(void* param)
{
 while (1)
 {
  CheckConnection(); //检查连接状况
  Sleep(2000);  //2s检查一次
 }

 return 0;
}

//接受请求
unsigned __stdcall ThreadAccept(void* param)
{
 _beginthreadex(NULL, 0, ThreadManager, NULL, 0, NULL);
 Init(); //初始化一定不要再while里面做，否则head会一直为NULL！！！
 while (1)
 {
  //创建一个新的客户端对象
  pClient pclient = (pClient)malloc(sizeof(_Client));

  //如果有客户端申请连接就接受连接
  if ((pclient->sClient = accept(g_ServerSocket, (SOCKADDR*)&g_ClientAddr, &g_iClientAddrLen)) == INVALID_SOCKET)
  {
   printf("accept failed with error code: %d\n", WSAGetLastError());
   closesocket(g_ServerSocket);
   WSACleanup();
   return -1;
  }
  recv(pclient->sClient, pclient->userName, sizeof(pclient->userName), 0); //接收用户名和指定聊天对象的用户名
  recv(pclient->sClient, pclient->ChatName, sizeof(pclient->ChatName), 0);

  memcpy(pclient->IP, inet_ntoa(g_ClientAddr.sin_addr), sizeof(pclient->IP)); //记录客户端IP
  pclient->flag = pclient->sClient; //不同的socke有不同UINT_PTR类型的数字来标识
  pclient->Port = htons(g_ClientAddr.sin_port);
  AddClient(pclient); //把新的客户端加入链表中

  printf("Successfuuly got a connection from IP:%s ,Port: %d,UerName: %s , ChatName: %s\n",
   pclient->IP, pclient->Port, pclient->userName,pclient->ChatName);

  if (CountCon() >= 2)      //当至少两个用户都连接上服务器后才进行消息转发 
   StartRecv();

  Sleep(2000);
 }
 return 0;
}

//启动服务器
int StartServer()
{
 //存放套接字信息的结构
 WSADATA wsaData = { 0 };
 SOCKADDR_IN ServerAddr = { 0 };    //服务端地址
 USHORT uPort = 18000;      //服务器监听端口

 //初始化套接字
 if (WSAStartup(MAKEWORD(2, 2), &wsaData))
 {
  printf("WSAStartup failed with error code: %d\n", WSAGetLastError());
  return -1;
 }
 //判断版本
 if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2)
 {
  printf("wVersion was not 2.2\n");
  return -1;
 }
 //创建套接字
 g_ServerSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
 if (g_ServerSocket == INVALID_SOCKET)
 {
  printf("socket failed with error code: %d\n", WSAGetLastError());
  return -1;
 }

 //设置服务器地址
 ServerAddr.sin_family = AF_INET;//连接方式
 ServerAddr.sin_port = htons(uPort);//服务器监听端口
 ServerAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);//任何客户端都能连接这个服务器

 //绑定服务器
 if (SOCKET_ERROR == bind(g_ServerSocket, (SOCKADDR*)&ServerAddr, sizeof(ServerAddr)))
 {
  printf("bind failed with error code: %d\n", WSAGetLastError());
  closesocket(g_ServerSocket);
  return -1;
 }
 //设置监听客户端连接数
 if (SOCKET_ERROR == listen(g_ServerSocket, 20000))
 {
  printf("listen failed with error code: %d\n", WSAGetLastError());
  closesocket(g_ServerSocket);
  WSACleanup();
  return -1;
 }

 _beginthreadex(NULL, 0, ThreadAccept, NULL, 0, 0);
 for (int k = 0;k < 100;k++) //让主线程休眠，不让它关闭TCP连接.
  Sleep(10000000);

 //关闭套接字
 ClearClient();
 closesocket(g_ServerSocket);
 WSACleanup();
 return 0;
}

int main()
{
 StartServer(); //启动服务器

 return 0;
}

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <WinSock2.h>
#include <process.h>
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#pragma comment(lib,"ws2_32.lib")
#define RECV_OVER 1
#define RECV_YET 0
char userName[16] = { 0 };
char chatName[16] = { 0 };
int iStatus = RECV_YET;
//接受数据
unsigned __stdcall ThreadRecv(void* param)
{
 char buf[128] = { 0 };
 while (1)
 {
  int ret = recv(*(SOCKET*)param, buf, sizeof(buf), 0);
  if (ret == SOCKET_ERROR)
  {
   Sleep(500);
   continue;
  }
  if (strlen(buf) != 0)
  {
   printf("%s\n", buf);
   iStatus = RECV_OVER;
  }
  else
   Sleep(100); 


 }
 return 0;
}

//发送数据
unsigned __stdcall ThreadSend(void* param)
{
 char buf[128] = { 0 };
 int ret = 0;
 while (1)
 {
  int c = getch();
  if (c == 27) //ESC ASCII是27
  {
   memset(buf, 0, sizeof(buf));
   printf("Please input the chat name:");
   gets_s(buf);
   char b[17] = { 0 };
   sprintf(b, "#%s", buf);
   ret = send(*(SOCKET*)param,b , sizeof(b), 0);
   if (ret == SOCKET_ERROR)
    return 1;
   continue;
  }
  if(c == 72 || c == 0 || c == 68)//为了显示美观，加一个无回显的读取字符函数
   continue;     //getch返回值我是经过实验得出如果是返回这几个值，则getch就会自动跳过，具体我也不懂。
  printf("%s: ", userName);
  gets_s(buf);
  ret = send(*(SOCKET*)param, buf, sizeof(buf), 0);
  if (ret == SOCKET_ERROR)
   return 1;
 }
 return 0;
}



//连接服务器
int ConnectServer()
{
 WSADATA wsaData = { 0 };//存放套接字信息
 SOCKET ClientSocket = INVALID_SOCKET;//客户端套接字
 SOCKADDR_IN ServerAddr = { 0 };//服务端地址
 USHORT uPort = 18000;//服务端端口
 //初始化套接字
 if (WSAStartup(MAKEWORD(2, 2), &wsaData))
 {
  printf("WSAStartup failed with error code: %d\n", WSAGetLastError());
  return -1;
 }
 //判断套接字版本
 if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2)
 {
  printf("wVersion was not 2.2\n");
  return -1;
 }
 //创建套接字
 ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
 if (ClientSocket == INVALID_SOCKET)
 {
  printf("socket failed with error code: %d\n", WSAGetLastError());
  return -1;
 }
 //输入服务器IP
 printf("Please input server IP:");
 char IP[32] = { 0 };
 gets_s(IP);
 //设置服务器地址
 ServerAddr.sin_family = AF_INET;
 ServerAddr.sin_port = htons(uPort);//服务器端口
 ServerAddr.sin_addr.S_un.S_addr = inet_addr(IP);//服务器地址

 printf("connecting......\n");
 //连接服务器
 if (SOCKET_ERROR == connect(ClientSocket, (SOCKADDR*)&ServerAddr, sizeof(ServerAddr)))
 {
  printf("connect failed with error code: %d\n", WSAGetLastError());
  closesocket(ClientSocket);
  WSACleanup();
  return -1;
 }
 printf("Connecting server successfully IP:%s Port:%d\n",
  IP, htons(ServerAddr.sin_port));
 printf("Please input your UserName: ");
 gets_s(userName);
 send(ClientSocket, userName, sizeof(userName), 0);
 printf("Please input the ChatName: ");
 gets_s(chatName);
 send(ClientSocket, chatName, sizeof(chatName), 0);
 printf("\n\n");

 _beginthreadex(NULL, 0, ThreadRecv, &ClientSocket, 0, NULL); //启动接收和发送消息线程
 _beginthreadex(NULL, 0, ThreadSend, &ClientSocket, 0, NULL);
 for (int k = 0;k < 1000;k++)
  Sleep(10000000);
 closesocket(ClientSocket);
 WSACleanup();
 return 0;
}

int main()
{
 ConnectServer(); //连接服务器
 return 0;
}