The principle focus of this publish is to make Java builders acquainted with low-level components like how TCP and UDP protocol works, socket choices and writing multi-threaded servers in Java.
The questions mentioned right here are usually not actually tied up with Java programming language and can be utilized in any programming language, which permits programmers to put in writing client-server functions.
By the best way, In case you are going for an interview on Funding banks for a core Java developer position, you higher put together effectively on Java NIO, Socket Programming, TCP, UDP, and Networking together with different in style subjects like multi-threading, Collections API, and Rubbish Assortment tuning. It’s also possible to contribute any query, which is requested to you or associated to socket programming and networking and may be helpful for Java interviews.
15 Finest Java Networking and Socket Programming Questions with Solutions for 3 to five Years Skilled Programmers
Right here is my checklist of 15 interview questions associated to networking fundamentals, web protocol, and socket programming in Java. Although it does not include primary questions from APIs like Server, ServerSocket, it focuses on the high-level idea of writing the scalable server in Java utilizing NIO selectors and how one can implement that utilizing threads, their limitations, and points, and many others.
I’ll in all probability add a couple of extra questions primarily based on some greatest practices whereas writing socket-based functions in Java. If you understand an excellent query on this matter, be happy to recommend.
1. What’s distinction between TCP and UDP protocol?
Due to this assure, TCP is slower than UDP, because it must carry out extra work. TCP is greatest suited to the message, which you’ll’t afford to lose, like. order and commerce messages in digital buying and selling, wire switch in banking and finance, and many others. UDP is extra suited to media transmission, the place the lack of one packet, referred to as datagrams is reasonably priced and does not have an effect on the standard of service.
This reply is sufficient for many of the interviews, however it’s good to be extra detailed if you end up interviewing as Java developer for a high-frequency buying and selling desk. Among the factors which many candidates overlook to say is about order and knowledge boundary.
In TCP, messages are assured to be delivered in the identical order as they’re despatched however knowledge boundary shouldn’t be preserved, which implies a number of messages may be mixed and despatched collectively, or receiver might obtain one a part of the message in a single packet and different components of the message in subsequent packet.
Although the appliance will obtain the total message and in the identical order. TCP protocol will do the assembling of message for you. However, UDP sends a full message in a datagram packet, if purchasers obtain the packet it’s assured that it’s going to get the total message, however there isn’t a assure that the packet will are available in the identical order they’re despatched.
In brief, you have to point out the next variations between TCP and UDP protocol whereas answering in the course of the interview :
- TCP is assured supply, UDP shouldn’t be assured.
- TCP ensures order of messages, UDP does not.
- Information boundary shouldn’t be preserved in TCP, however UDP preserves it.
- TCP is slower in comparison with UDP.
for a extra detailed reply, see my publish 9 variations between TCP and UDP protocol.
2. How does TCP handshake works?
3. How do you implement dependable transmission in UDP protocol?
If the receiver finds that it has missed a sequence quantity, it might ask for a replay of that message from the Server. TRDP protocol, which is used Tibco Rendezvous (a preferred excessive pace messaging middle-ware) makes use of UDP for sooner messaging and gives reliability assure by utilizing sequence quantity and retransmission.
4. What’s Community Byte Order? How do two hosts talk if they’ve totally different byte-ordering?
There are two methods to retailer two bytes in reminiscence, little-endian (least vital byte on the beginning tackle) and big-endian (most important byte on the beginning tackle). They’re collectively referred to as host byte order.
IBM PowerPC processors would retailer the integer within the byte order 4-3-2-1. Networking protocols corresponding to TCP are primarily based on a particular community byte order, which makes use of big-endian byte ordering. If two machines are speaking with one another they usually have totally different byte ordering, they’re transformed to community byte order earlier than sending or after receiving.
Subsequently, a little-endian micro-controller sending to a UDP/IP community should swap the order through which bytes seem inside multi-byte values earlier than the values are despatched onto the community, and simply swap the order through which bytes seem in multi-byte values acquired from the community earlier than the values are used. In brief, you can even say community byte order is the usual of storing bytes throughout transmission, and it makes use of a big-endian byte ordering mechanism.
5. What’s Nagle’s algorithm?
Since small packets, which include just one or 2 bytes of information, has extra overhead by way of TCP header, which is 40 bytes. These small packets may also result in congestion in a gradual community. Nagle’s algorithm tries to enhance the effectivity of TCP protocol by buffering them, to ship a bigger packet.
Additionally, Nagle’s algorithm has a adverse impact on non-small writes, so in case you are writing massive knowledge on packets then it is higher to disable Nagle’s algorithm.
Normally, Nagle’s algorithm is a protection in opposition to the careless software, which sends plenty of small packets to the community, but it surely is not going to profit or have a adverse impact on well-written functions, which correctly takes care of buffering.
Right here can also be a pleasant diagram which explains the community visitors with and with out Nagle’s algorithm:
6. What’s TCP_NODELAY?
The place a learn after two successive writes on the socket might get delayed as much as 500 milliseconds till the second write has reached the vacation spot.
7. What’s multicasting or multicast transmission? Which Protocol is mostly used for multicast? TCP or UDP?
Tibco Rendezvous helps multicast transmission. Multi-casting can solely be applied utilizing UDP as a result of it sends full knowledge as a datagram bundle, which may be replicated and delivered to different subscribers. Since TCP is a point-to-point protocol, it cannot ship messages to a number of subscribers, till it has the hyperlink between every of them.
Although UDP shouldn’t be dependable, and messages could also be misplaced or delivered out of order. Dependable multicast protocols corresponding to Pragmatic Normal Multicast (PGM) have been developed so as to add loss detection and retransmission on high of IP multicast.
IP multicast is broadly deployed in enterprises, business inventory exchanges, and multimedia content material supply networks. Widespread enterprise use of IP multicast is for IPTV functions
Here’s a good diagram which explains how multicasting works:
8. What’s the distinction between Matter and Queue in JMS?
The principle distinction between Matter and Queue in Java Messaging Service is that Queue is used for level to level communication which is mostly one to 1, whereas writer is used for publish and subscribe communication which is one to many.
9. What’s the distinction between IO and NIO in Java?
The principle distinction between NIO and IO is that NIO gives asynchronous, non-blocking IO, which is essential to put in writing sooner and scalable networking programs. Whereas many of the utility from IO lessons are blocking and gradual.
NIO takes benefit of asynchronous system calls in UNIX programs corresponding to choose() system name for community sockets. Utilizing choose(), an software can monitor a number of sources on the identical time and may also ballot for community exercise with out blocking.
10. How do you write a multi-threaded server in Java?
A multi-threaded server is one that may serve a number of purchasers with out blocking. Java gives wonderful assist to builders corresponding to servers. Previous to Java 1.4, you possibly can write a multi-threaded server utilizing conventional socket IO and threads.
Although this design may be improved by utilizing thread swimming pools and employee threads, it’s nonetheless a resource-intensive design. After JDK 1.4 and NIO’s introduction, writing scalable and multi-threaded servers grow to be a bit simpler. You possibly can simply create it in a single thread by utilizing Selector, which takes benefit of the asynchronous and non-blocking IO mannequin of Java NIO.
11. What’s the ephemeral port?
In TCP/IP connection normally incorporates 4 issues, Server IP, Server port, Consumer IP, and Consumer Port. Out of those 4, 3 are well-known more often than not, what shouldn’t be identified is consumer port, that is the place ephemeral ports come into the image.
These are short-lived, non permanent ports, which may be reused as soon as the connection is closed, however most of IP software program does not reuse ephemeral port till the entire vary is exhausted. Much like TCP, UDP protocol additionally makes use of an ephemeral port, whereas sending datagram.
12. What’s the sliding window protocol?
Sliding window protocol is a way for controlling transmitted knowledge packets between two community computer systems the place dependable and sequential supply of information packets is required, corresponding to offered by the Transmission Management Protocol (TCP).
Within the sliding window approach, every packet features a distinctive consecutive sequence quantity, which is utilized by the receiving laptop to put knowledge within the appropriate order. The target of the sliding window approach is to make use of the sequence numbers to keep away from duplicate knowledge and to request lacking knowledge
13. When do you get the “too many information open” error?
14. What’s TIME_WAIT state in TCP protocol? When does a socket connection go to TIME_WAIT state?
When one finish of TCP Connection closes it by making a system name, it goes into TIME_WAIT state. Since TCP packets can arrive within the incorrect order, the port should not be closed instantly to permit late packets to reach. That is why that finish of TCP connection goes into TIME_WAIT state.
15. What is going to occur when you’ve got too many socket connections within the TIME_WAIT state on the Server?
That is all about on this checklist of networking and socket programming interview questions and solutions. Although I’ve initially supposed this checklist for Java programmers it’s equally helpful for any programmer.
One purpose for this can be as a result of Java programmers have gotten so many helpful libraries like Apache MINA, which does all of the low-level work for them. Anyway, information of fundamentals is essential and all the things else is simply an excuse, however sooner or later, I additionally suggest utilizing tried and examined libraries like Apache MINA for manufacturing code.
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