TCP套接字不会在c中接收数据

Question

I got the task to create some Chat Client. The server is given and code unknown (only got the executable). The Client/Server communicates via TCP. First the Client connects to the server and sends his username. The Server will answer with some Statuscode. At this state I'm stuck. I created the socket and connect to the server. The server shows, that it receives the username but my client doesn't get any answer.

#define MAX_USERNAME    11
#define MAX_MSG_SIZE    1001
#define SERVERIP        "localhost" 
#define SERVERPORT      5000

[...]someFunctions()[...]

int _tmain(int argc, char* argv[])
{
    char defaulthost[] =    "localhost";
    hostent                 *host;
    protoent                *protocol;
    SOCKADDR_IN             server_addr;
    SOCKET                  socket_d;
    unsigned short          port;
    char                    *hostname;
    int                     n;
    int                     c;
    int                     connectCode;
    char username[MAX_USERNAME];
    char message[MAX_MSG_SIZE];

    long                        conn;
    long                        msgSize;

    [...]
    //read in username
    [...]

    // Connect to Server

    RNP_Init(); // intializes winsock

    memset(&server_addr, 0, sizeof(server_addr));       
    server_addr.sin_family = AF_INET;                   
    port = SERVERPORT;                                  
    if (port > 0){            
        server_addr.sin_port = htons(port);             
    }
    else {                                              
        fprintf(stdout,"Ungültige Portnummer\n");
        RNP_Cleanup();
        exit(EXIT_FAILURE);
    }

    hostname = defaulthost;
    conn = getAddress(hostname,&server_addr);
    if(conn == SOCKET_ERROR){
        fprintf(stdout,"IP fuer %s nicht aufgeloest",hostname);
        RNP_Cleanup();
        exit(EXIT_FAILURE);
    }
    else{
        fprintf(stdout,"IP aufgeloest");
    }

    socket_d = socket(AF_INET, SOCK_STREAM, 0); 
    if (socket_d == INVALID_SOCKET) {
        RNP_Error(RNP_E_SOCK, "Fehler bei Generierung des Sockets\n");
        RNP_Cleanup();
        exit(EXIT_FAILURE);
    }
    else  {
        fprintf(stdout, "Socket erfolgreich erstellt!\n");
    } 

    conn = connect(socket_d, (SOCKADDR*)&server_addr,sizeof(SOCKADDR));

    if(conn==SOCKET_ERROR){
        printf("Fehler: connect gescheitert, ERROR: %d\n", WSAGetLastError());
        RNP_Cleanup();
        fprintf(stdout,"Taste druecken zum beenden\n");
        getch();
        exit(EXIT_FAILURE);
    }
    else{
        printf("Verbunden mit Server!!\n");
    }

    while(conn != SOCKET_ERROR) {
        fprintf(stdout,"Sende Nutzernamen...\n");
        send(socket_d, username, strlen(username), 0);
        fprintf(stdout,"Username gesendet: %s mit der Laenge %d\n", username, strlen(username));

        msgSize = recv(socket_d,message,1001,0);
        if(msgSize==0){
            fprintf(stdout,"Verbindung vom Server getrennt\n");
            break;
        }
        if(msgSize==SOCKET_ERROR){
            fprintf(stdout,"Error: %d\n",WSAGetLastError());
            break;
        }
        message[conn]='\0';
        printf("Server antwortet: %s\n",message);
    }
[...]

Answer 1

The problem is here:

message[conn]='\\0';

If conn equals 0, you will not be able to "see" the data. You should not use conn but msgSize , which contains the number of received bytes.

message[msgSize]='\\0';

EDIT: You should take care of Barmar 's advices.