QLocalServer在字节不可用时发出readyRead

Question

我正试图在本地OSX 10.11中启动QLocalServer。

我有一个客户端，它尝试循环连接到服务器：

int connect(const char* filename) {
  int sock;
  struct sockaddr_un serv_addr;
  memset(&serv_addr, 0x00, sizeof(serv_addr));
  serv_addr.sun_family = AF_LOCAL;
  strncpy(serv_addr.sun_path, filename, sizeof(serv_addr.sun_path) - 1);
  if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
    return sock;
  }
  if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1) {
    close(sock);
    sock = -1;
    return sock;
  }
  return sock;
}
int main() {
  int sock;
  while((sock = connect("my_socket_server")) == -1) {
    usleep(3000);
  }
  // The code never reaches this line
  const char* buffer = "hello";
  if (send(sock, buffer, strlen(buffer), 0) < 0) {
    exit(1);
  }
  return 0;
}

当这段代码运行时，我尝试在另一个应用程序中启动QLocalServer：

// Starting server:
QString socket_path = "my_socket_server";
QLocalServer::removeServer(socket_path);
if (!server.listen(socket_path)) {
  return false;
}
connect(&server, &QLocalServer::newConnection, this, &MyServerClass::newConnection);
...
void MyServerClass::newConnection() {
  socket = server.nextPendingConnection(); // socket - member of MyServerClass
  connect(socket, &QLocalSocket::disconnected, socket, &QLocalSocket::deleteLater);
  connect(socket, &QLocalSocket::readyRead, this, &MyServerClass::readyRead);
}
...
void MyServerClass::readyRead() {
  if (!socket->bytesAvailable()) {
    exit(1); // THIS CODE WAS CALLED. WHY?
  }
  ...
}

为什么在调用readyRead时，字节不可用？

Answer 1

您可能得到多个连接，在这种情况下，socket变量可能指向与发出readyRead信号的对象不同的对象。使用QObject::sender在插槽中获取正确的对象，或者使用QSignalMapper。如果使用Qt5，还可以使用lambda函数并捕获socket对象。