Socket programming issue, data sent on exit

I've a problem with socket programming on OS X (C++). My client can connect to the server, but when I send data, despite the send() doesn't fail, the data are sent only when the program exits.

Here is my code :

creation of the socket and connection to server in the client constructor :

ComBridge::ComBridge(std::string comManagerIP, int portNumber){
    this->myComManagerIP = comManagerIP;
    this->portNum = portNumber;

    initComBridge();
}

ComBridge::~ComBridge(){
   close(socketFD);
}

void ComBridge::initComBridge(){
    /*Opening the socket*/
    socketFD = socket(AF_INET, SOCK_STREAM, 0);
    if (socketFD<0) {
        cout<<"Error opening socket !"<<endl;
        exit(1);
    }

    /*Defining the server address*/
    bzero((char *) &server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    /*bcopy(myComManagerIP.c_str(),
      (char *)&server_addr.sin_addr.s_addr,
      myComManagerIP.size());*/
    inet_pton(AF_INET,myComManagerIP.c_str(),&server_addr.sin_addr);
    server_addr.sin_port = htons(portNum);

    cout<<"ip server store : "<<myComManagerIP.c_str()<<endl;

    cout<<"ip server in server_addr: "<<server_addr.sin_addr.s_addr<<endl;

    /*Connecting to ComManager*/
    int rcon = connect(socketFD, (struct sockaddr*)&server_addr, sizeof(server_addr));
    cout<<"back num for connection : "<<rcon<<endl;
    if (rcon<0) {
        cout<<"Failed connection to ComManager !"<<endl;
    }
}

And the sending and receiving methods :

void ComBridge::readMessage(){
    bzero(bufferIn,256);

    /*Waiting for data from socket*/
    ssize_t numOfCharRecv = recv(socketFD, &bufferIn, 255,0);
    //ssize_t numOfCharRecv = read(socketFD,&bufferIn,255);

    if (numOfCharRecv < 0)
        cout<<"ERROR reading socket"<<endl;

    /*Storing the string received in a jsonDocument*/
    jsonDocument.Parse(bufferIn);
    cout<<"message : "<<bufferIn<<endl;
    /*Notifying observers of event*/
    //notify(jsonDocument);
}

void ComBridge::writeMessage(rapidjson::Document& d){
    buffer = myJsonHandler.convertJsonToString(d);

    cout<<buffer<<endl;

    ssize_t writeRes = send(socketFD,buffer.c_str(),strlen(buffer.c_str())+1,0);
    if (writeRes < 0)
        cout<<"ERROR writing to socket"<<endl;
    else cout<<"Message sent ! "<<writeRes<<endl;
}

Has anyone an idea of what's wrong ?

Thanks for help !

Mikael10j