In computer networking, to represent data, “Seven layer architecture” is used, which was developed by the International Standard Organization which is commonly termed as ISO. Among the seven layers the third layer is network layer. In this layer the PDU format that is the data format is packet. It means the data is transferred in this layer by exchanging packets among a number of hosts. Many ports are used in the transport layer that is in the forth layer of ISO to accept data. A commonly used protocol in this layer is TCP that means transmission control protocol. It accepts packets from different hosts which are exist in the specific network. There are two types of TCP ports those are generally used to control reliable data transmission over a network. The names of these two TCP ports are open port and closed port. The open ports are used in a network to accept all the packets which are coming from the other hosts of the specific network. In case of closed port, all the packets are ignored to accept. These ports are generally used for security purpose. At this present updating era many networks are affected by the activities of hackers. So to protect a network from these hackers network security is required. To reject the packets which are coming from the other danger network the concept of closed port is used. But before accepting these packets open ports are generally tests the packets. Before making a reliable data transmission through a network with TCP/IP networking it is required to grant the port by the network. In case of closed port TCP network this facility is disabled by the network. So packet transfer is not possible in this type of networking. So a reliable data transmission can't be made in this type of networking, but to perform confidential data transmission among a minimum number of hosts this type of ports are ideal. Because, this type of networking is more secure than any other process of networking. But at this modern updating era the use of open port becomes wider. After introducing WAN that is wide area networking this open ports are used by the maximum number of hosts in a network to exchange their packets that means to provide a reliable data transmission over a network. On internet, many tools are available to provide open port facilities. Open port tool is becomes one of the most popular online tools at this present world.