在一台服務器上接收多個客戶端數據包

Question

我有3個應用程序，一台服務器，2個客戶端。 我正在嘗試對此編程，以便可以將登錄請求從客戶端發送到服務器，並請求查看有關另一個客戶端的信息。

問題：我為所有3個應用程序使用相同的ip和端口號（全部在計算機上的3個Visual Studio應用程序中完成），否則我認為它不會連接到服務器。 這個可以嗎？

當我嘗試在服務器的while循環之外使用listen和accept時，它僅對一個客戶端有效，而對另一個客戶端無效。 當我嘗試將監聽和接受放入while循環中時，它對兩個客戶端均有效，但不會響應多個接受。 我怎么了

服務器

struct Users {

int message;
char userName[50];
char ipAddress[50];
int PortNumber;
bool online;

};

int main () {

//Create users
Users client[2];

client[0].PortNumber = 20000;
client[0].online = false;
sprintf(&client[0].userName[0], "Albert");
sprintf(&client[0].ipAddress[0], "127.0.0.1");

client[1].PortNumber = 20000;
client[1].online = false;
sprintf(&client[1].userName[0], "Monique");
sprintf(&client[1].ipAddress[0], "127.0.0.1");


//Set up all the connection stuff
struct sockaddr_in SvrAddr;
SOCKET WelcomeSocket, ConnectionSocket;
int PortNumber = 20000;
int result;
char IPAddress[] = "127.0.0.1";
char RxBuffer[128];
char TxBuffer[128];


WORD wVersionRequested; 
WSADATA wsaData; 

wVersionRequested = MAKEWORD(2,2); //For Server 


if(WSAStartup(wVersionRequested, &wsaData) != 0) 
    return -1;


//Setting up the welcome socket
WelcomeSocket = socket(AF_INET, SOCK_STREAM, 0);

//Setting up the sockaddr svraddr structure
SvrAddr.sin_family = AF_INET;
SvrAddr.sin_addr.s_addr = inet_addr(IPAddress);
SvrAddr.sin_port = htons(PortNumber);


//Bind
bind(WelcomeSocket, (sockaddr*)&SvrAddr, sizeof(SvrAddr));

//listening
//listen(WelcomeSocket, 5);

//temp users
Users temp;
//ConnectionSocket = accept(WelcomeSocket, NULL, NULL);
ConnectionSocket = SOCKET_ERROR;

//while loop for the connection 
while (1) {

    listen(WelcomeSocket, 5);

    if ((ConnectionSocket = accept(WelcomeSocket, NULL, NULL)) == SOCKET_ERROR)
    {
        return -1;
    }

    else {

    int n = recv(ConnectionSocket, RxBuffer, sizeof(RxBuffer), 0);

    if (n == 0)
        break;


    memcpy(&temp, RxBuffer, sizeof(struct Users));

    //cout << temp.message << temp.userName << endl << endl;

    //check which message type is being sent
    switch(temp.message) {

    //if message type 1
    case 1 :
        for (int i = 0; i < 2; i++) {

            //if receieved username matches with any username in the database
            if (strcmp(temp.userName, client[i].userName) == 0) {

                //assign the recieved users information to the matched one in database
                strcpy(client[i].userName, temp.userName);
                client[i].online = true;
                client[i].message = 2;

                cout << "Username: " << client[i].userName << endl << "Online status: " << client[i].online << endl << endl;

                //send the acknowledgement packet
                send(ConnectionSocket, (char *)&client[i], sizeof(struct Users), 0);
                //closesocket(ConnectionSocket);
            }

        }
        break;

    //if message type 3
    case 3 :

        cout << "User being searched for: " << temp.userName << endl << endl;
        for (int i = 0; i < 2; i++) {

            //if receieved username matches with any username in the database
            if (strcmp(temp.userName, client[i].userName) == 0) {
                client[i].message = 4;
                //send the acknowledgement packet
                send(ConnectionSocket, (char *)&client[i], sizeof(struct Users), 0);
                //closesocket(ConnectionSocket);
            }

        }
        break;

    default :
        break;

    }

}

}

closesocket(ConnectionSocket);
WSACleanup();
}

客戶（兩者相同）

struct Users {

int message;
char userName[50];
char ipAddress[50];
int PortNumber;
bool online;

};


int main () {

struct sockaddr_in SvrAddr;
SOCKET ClientSocket;
int PortNumber = 20000;
char IPAddress[] = "127.0.0.1";
//char message[] = "Hello this is the client.";
char RxBuffer[128];

WORD wVersionRequested; 
WSADATA wsaData; 

wVersionRequested = MAKEWORD(2,3); //For Client 

if(WSAStartup(wVersionRequested, &wsaData) != 0) 
    return -1; 


ClientSocket = socket(AF_INET, SOCK_STREAM, 0);

SvrAddr.sin_family = AF_INET;
SvrAddr.sin_addr.s_addr = inet_addr(IPAddress);
SvrAddr.sin_port = htons(PortNumber);

connect(ClientSocket, (sockaddr*)&SvrAddr, sizeof(SvrAddr));



//cout << "Name: ";
//cin >> login;

//Send request to login
int log;
char * name = new char[128];
char * request = new char[128];
Users client;
Users talkto;


do {

    cout << "To login press (1) to end press (2). ";
    cin >> log;
    flushall();

    if (log == 1) {

        cout << "Username : ";
        cin.getline(name, 128, '\n');
        cout << endl;
        flushall();

        //Set client login info
        strcpy(client.userName, name);
        client.message = 1;



        send(ClientSocket, (char *)&client, sizeof(struct Users), 0);


        //Recieve acknowledgement
        recv(ClientSocket, RxBuffer, sizeof(RxBuffer), 0);
        //create temp users
        Users temp;

        memcpy(&temp, RxBuffer, sizeof(struct Users));

        //If logged in and received a message of type 2 (acknowledgement)
        if (temp.message == 2) {

            cout << "You have logged in." << endl << endl;

            cout << "Enter user to request user information: ";
            cin.getline(talkto.userName, 128, '\n');
            flushall();
            cout << endl;

            talkto.message = 3;

            //send request for user information packet
            send(ClientSocket, (char *)&talkto, sizeof(struct Users), 0);

            recv(ClientSocket, RxBuffer, sizeof(RxBuffer), 0);

            memcpy(&temp, RxBuffer, sizeof(struct Users));

            //if message received is of type 4 (acknowledgement of user request info)
            if (temp.message == 4) {

                cout << "Requested User: " << temp.userName << endl << "Online status: " << temp.online << endl << endl;
            }
        }

        //cout << temp.userName << endl << temp.online << endl << temp.message;
    } 

} while (log != 2);


closesocket(ClientSocket);


WSACleanup();



} 

Answer 1

您不要在循環內使用listen() 。 只有accept() 。 您也不要使用nonblocking socket ，但這是您的偏愛。 另一件事，每次完成accept都必須使用closesocket 。 同樣，您的recv()必須循環處理，因為與send不同，它可能在接收所有數據之前返回。

服務器的基本結構：

struct sockaddr_in inAddr; //incoming address. Use it to distinguise between incoming clients
struct sockaddr_in address;
unsigned int inLen;
int recvMsgSize;
unsigned short port = 20000;
Socket socket_handle, acceptSocket;

socket_handle = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(socket_handle == INVALID_SOCKET){
    //error
}

memset(&address, 0, sizeof(address));
address.sin_family = AF_INET;
address.sin_addr.s_addr = htonl(INADDR_ANY); //All incoming addresses
address.sin_port = htons(port); //port must be unsigned short not int!
if(bind(socket_handle, (struct sockaddr *)&address, sizeof(address)) < 0){
    //error
}

if(listen(socket_handle, MAXPENDING) < 0){
    //error
}

while(true){
    acceptSocket = accept(socket_handle, (struct sockaddr *) &inAddr, &inLen));
    if(acceptSocket == INVALID_SOCKET){
        //error
    }

    while(true){
        recvMsgSize = recv(acceptSocket, received_data, strlen(received_data), 0);
        if(recvMsgSize < 0){/*error*/}
        else if(recvMsgSize == 0){break;}
        else{/*receive your data*/}
    }

    (do other stuff...)
    closesocket(acceptSocket);
}

closesocket(socket_handle);
WSACleanup();

瓦爾特