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What is TFTP?TFTP stands for Trivial File Transfer Protocol. This protocol is used when users need to copy their files. In other words, it allows the user to store and access their files from the remote host. It is mainly used for the booting system. To understand this concept, let us take a simple example, Suppose you have a booted diskless system or router; for that, you need to download bootstrap files and configurations files. In that situation, you need a protocol to copy those files at a faster speed. Here the TFTP comes into the picture. It is designed to copy these types of files.
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It requires only IP (Internet Protocol) and UDP (User Datagram Protocol). It performs two operations, read and write, namely. In a read operation, it copies files from server SIDE yo client SIDE, while in a write operation, it works exact oppoSIDE; it copies files from client-side to the server-side.
It uses UDP services on the well-known port 69.
Types of TFTP MessagesThere are five types of TFTP message listed below:
RRQ
WRQ
DATA
ACK
ERROR
1) RRQ messageRRQ stands for the read request message. The client uses this to create a connection For reading data from the server SIDE. RRQ message has three fields OpCode, Filename and Mode. An OpCode is a 2 byte in size; It contains 1 to show the RRQ message. Filename defines the name of the file. Modes define the transmission mode. Transmission mode can be netascii for ASCII file or octet for binary files. The message format of RRQ is given as follows.
2) WRQ messageWRQ stands for the write request message. The client uses this to create a connection for writing data from the server SIDE. WRQ message has the same fields as RRQ, only difference because OpCode contains 2 to show the WRQ message. Here we can see the WRQ message format.
3) DATA messageBoth client and server use data messages to send data blocks. Data contains three fields – OpCode, Block number, and Data. OpCode contains 3 to show data messages. A Block number is a 2-byte field that contains a block number. All blocks are sequentially numbered from 1. The client and server use this field to send data sequentially so that the receiver will combine the whole message using this block number. Data is of 512 bytes. Data can be transferred in the form of netascii (ASCII file) or octet (Binary file). The DATA message format is given as follows.
4) ACK messageACK stands for Acknowledge message. Both client and server use this ACK to acknowledge the receipt of the data block. This message is of 4 bytes. It contains two fields – OpCode and Block number. OpCode contains 4 to show the ACK message. Block number is of a 2-byte field that contains the number of data blocks received. ACK message can also respond to the WRQ message, which is sent by a server to the client for indicating that the server is ready to receive data from the client. ACK message format is given as follows.
5) ERROR messageClient and server use ERROR message when a connection between client and server cannot be established or when some error has occurred during data transmission. It sends a negative response to the RRQ message or WRQ message. This message contains three fields – Oe, Error number and Error data. OpCode contains 5 to show the ERROR message. The error number is of 2 byte that contains the error number and its meaning. The ERROR message format is given as follows.
Below is the list of error number with their meaning
1 – File not found
2 – Access violation
3 – Disk full or quota exceeded
4 – Illegal operation
5 – Unknown port number
7 – No such user
The error data field contains error data in text format. It is a 1-byte field and terminated by 0s.
TFTP ConnectionsIt uses an RRQ message, WRQ message, ACK message, and ERROR message to establish connections. While terminating connections, TFTP uses the DATA message.
1) Connection EstablishmentThe process of connection establishment for reading files is different from writing files.
Reading: The client sends the RRQ message to establish a connection for reading. This message contains the name of the file and the transmission mode of the file. Once the connection is established, the server sends a positive response with the DATA message if the server is able to transfer the file. Suppose it does not then send a negative response with an ERROR message.
Writing: The client sends WRQ messages to establish a connection for writing. This message contains the name of the file and the transmission mode of the file. Once the connection is established, the server sends a positive response with an ACK message if the server is able to copy the file. Suppose it does not then send a negative response with an ERROR message.
Here is the representation of reading and writing operation
2) Connection TerminationAfter the transmission of the file, the connection must be terminated. It does not use a special message to terminate the connection. Termination is done by sending the last data block, which is less than 512 bytes.
Recommended ArticlesThis is a guide to TFTP. Here we have discussed an overview of different types of TFTP messages, how the TFTP connections established, and termination that made it easy to understand the concepts. You may also look at the following article to learn more –
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How To Increase The Number Of Remote Desktop Connections In Windows 11/10
In general, Windows 11/10 lets you establish only one Remote Desktop Connection on one computer. However, with a few tweaks, you can establish more than one Remote Desktop Connections on a Windows system. This can be useful if you see a You have been disconnected because another connection was made to the remote computer message.
How many connections can you establish via RDP?In normal conditions, Windows 11/10 restricts the number of users who can connect via Remote Desktop Connection. By default, this number is 1. If another user tries to connect when one Remote Desktop Connection is already established, then the new user gets an error message. The error message says-
Another user is signed in. If you continue, they’ll be disconnected. Do you want to sign in any way?
To avoid this, you can increase the number of users who can log into Remote Desktop service simultaneously.
Read: Can you enable Concurrent Sessions in Windows 11/10?
Increase the number of Remote Desktop ConnectionsNeed to allow multiple Remote Desktop Connections in Server? You can allow more than two RDP sessions in Windows 11/10 by making use of a Gropu Policy setting.
Here are the steps with the help of which you can increase or limit the number of Remote Desktop Connections in Windows 11/10.
1] Press Start Menu and start typing chúng tôi .
2] Now, open this console. It opens the Local Group Policy Editor window.
3] Now, follow the next steps:
You will see the following list in the open right-hand side panel.
5] Select the Enabled radio button to increase or limit the number of Remote Desktop Connections. This enables the counter menu of ‘RD Maximum Connections allowed’ in the Options section.
6] Now, increase or decrease the maximum number of connections allowed in the counter using the up or down arrow, as per the requirement.
You will see the following information on the right-hand side panel of Help.
This setting specifies whether Remote Desktop Services limits the number of simultaneous connections to the server.
You can use this setting to restrict the number of Remote Desktop Services sessions that can be active on a server. If this number is exceeded, additional users who try to connect receive an error message telling them that the server is busy and to try again later. Restricting the number of sessions improves performance because fewer sessions are demanding system resources. By default, RD Session Host servers allow an unlimited number of Remote Desktop Services sessions, and Remote Desktop for Administration allows two Remote Desktop Services sessions.
To use this setting, enter the number of connections you want to specify as the maximum for the server. To specify an unlimited number of connections, type 999999.
If the status is set to Enabled, the maximum number of connections is limited to the specified number consistent with the version of Windows and the mode of Remote Desktop Services running on the server.
If the status is set to Disabled or Not Configured, limits to the number of connections are not enforced at the Group Policy level.
This setting is designed to be used on RD Session Host servers (that is, on servers running Windows with Remote Desktop Session Host role service installed).
After this, you will see the state of ‘Limit number of connection’ is changed to ‘Enabled’.
To restore the settings, go through the same steps.
Restart your computer for the changes to take effect.
Related: Remote Credential Guard protects Remote Desktop credentials.
Different Types Of Operators In Postgresql
Introduction to PostgreSQL Operators
PostgreSQL Operators is a database management system and open-source software that enables easy access for the public to use for relational database purposes. Relational Database purposes are data manageability to explain it in a nutshell.
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PostgreSQL OperatorsBelow are the different PostgreSQL Operators, which are as follows:
1. Logical OperatorsIn PostgreSQL, the logical operators consist of the general operators, namely, logical operators are used to perform the logical operations described below.
OR
AND
NOT
a. OR OperatorOR The operator returns TRUE if either value of an operand is TRUE.
Values passed as logic can be applied in different combinations to gain desired results.
So let us look at the truth table below.
We can assume 0 is FALSE and 1 as TRUE. Hence 0 or 1 is 1, which is essentially TRUE.
We can see that the OR operator returns FALSE (0) only when both X and Y are FALSE.
X
Y
X OR Y
0
0 0
0
1
1
1
0
1 1
1
b. AND OperatorAND The operator returns TRUE only if the values of all operands are TRUE.
Unlike the OR operator, AND operator returns TRUE (1) only when both X and Y are TRUE.
X
Y
X AND Y
0
0
0
0
1
0
1
0
0
1
1 1
c. NOT OperatorNOT This operator negates the initial value of an operand. If the operand value is TRUE, then FALSE is returned.
Regarding the NOT operator, the logic is that the operator returns FALSE if the operand is TRUE and vice versa.
X
NOT(X)
0
1
1
0
2. Arithmetic Operators/Mathematical OperatorsArithmetic operators perform specific mathematical operations like addition, subtraction, etc. In PostgreSQL, Arithmetic operators are used to perform the Arithmetic operations as described below.
Operator Name
Operators
Functionality
Example
Result
Addition
+
Adds values of operands 10 +11 21
Subtraction
–
Subtracts values of operands 10 -11 -1
Multiplication
*
Performs multiplication on operands 10 * 11 110
Division
/
Performs Division on operands 10/5 2
Modulo
%
Performs Division but returns the remainder as output 11%10 1
Exponentiation
^
This provides the power value of the desired operand 10^2 100
Square Root
Performs Square Root of an operand |/ 16 4
Cube Root
Performs Cube root of an operand ||/64 4
Factorial
!
Returns factorial of a given number (Postfix form) 4! 24
Factorial ( with prefix operator)
!!
Returns factorial of a given number (Prefix form) !! 4 24
3. Bitwise OperatorsTo understand Bitwise operators’ functionality, we need to know that these operators will work only on integrals and that the operator’s functionality takes place in the operand’s binary form (representation in 0s and 1s). In PostgreSQL, Bitwise operators are used to perform the Bitwise operators as described below.
Operators Example
Result
Bitwise AND
&
10 & 12 8
Bitwise OR
14
Bitwise NOT
~
~10 5
Bitwise XOR
#
10 # 12 6
Bitwise shift left
<<
10 << 2 40
Bitwise shift right
25
Let us take two operands, for example:
10 – Binary Representation is 1010.
12 – Binary Representation is 1100.
Refer below to how operands 10 and 12 get interpreted into their equivalent Binary form.
10 – Binary Representation is 1010
12 – Binary Representation is 1100
a. Bitwise AND OperatorThis operator interprets the operands in their binary representation and performs the AND function on every digit of the operands.
b. Bitwise OR OperatorThis operator interprets the operands in their binary representation and performs the OR function on every digit of the operands.
c. Bitwise Not OperatorThis operator performs the negation operation on each digit of the operand. It can take only one operand at a time; hence it is known as a unary operator.
In the above example, all 0S are converted to 1S and vice versa.
d. Bitwise XOR OperatorThis operator interprets the operands in their binary representation and performs the XOR function on every digit of the operands.
XOR function returns TRUE or 1 if either one of the operands is TRUE or 1
XOR function returns FALSE or 0 if all the operands are TRUE or all the operands are FALSE.
e. Bitwise Shift Left OperatorThis operator shifts the given number’s bits in its binary representation to the left side by a specified number of bits. Let us say the specified number of bits is x, then shift each bit of 10 to the left by x bits is denoted as 10 <<x. If x is 2, then 10 << 2 is 40.
f. Bitwise Shift Right Operator 4. Comparison OperatorsComparison Operators interpret an expression and provide output in Boolean values. (TRUE or FALSE). In PostgreSQL, Comparison Operators perform the Comparison Operators described below.
Some of the common Comparison operators are shown below.
Operator
Operator Name
<
Less than an operator
Greater than operator
=
Equals
not equals
<=
Less than or equal to the operator
Greater than or equal to the operator
a. Operator ‘<.’This operator compares the given expression and returns TRUE if the first operand is less than the second operand in the expression, or else it returns FALSE.
This operator compares the given expression and returns TRUE if the first operand is greater than the second operand in the expression, or else it returns FALSE.
c. Operator ‘=.’This operator compares the operands in the expression and returns TRUE if both operands are of the same value, or else it returns FALSE.
This operator compares the operands in the expression and returns TRUE if both operands are not of the same value or return FALSE.
e. Operator ‘<=.’This operator returns TRUE if the first operand’s value is lesser or equal to the value of the second operand.
This operator returns TRUE if the first operand’s value is greater or equal to the value of the second operand.
Recommended ArticlesWe hope that this EDUCBA information on “postgresql operators” was beneficial to you. You can view EDUCBA’s recommended articles for more information.
Types Of Joints In Optical Fiber
Optical fiber is a technology through which data passes in the form of light at high speed. It is a thin transparent cable type that is flexible and can be bent easily Fiber optics cable can be joined many times in one installation using joints. Joints are used to transfer light from one fiber optic cable to another fiber optic cable and are made up of plastic or glass material. In this article, we will explore the various types of Joints in Optical Fiber.
Types of joints in optical fiberUnlike the normal joints, these are the special joints used for fiber optic cables only and can be classified based on their characteristics as follows −
Splice
Mechanical splice
Fusion splice
Connector
DNP connector (Dry No Polish)
SMA connector (Sub Miniature type A)
Coupler
T-coupler
Star
Three ports coupler
SpliceSplice joints are used to connect the two ends of fiber optic cables permanently. It is used when two cables (for example 45- fiber cable and 22-fiber cable) are connected using a splice joint to form one long cable. This method is commonly used for signal transmission over a long distance.
Splice is of two types
Mechanical splice −
This joint uses a technique designed to hold two fiber ends in a position such that light passes through two fiber cables.
Fusion splice −
A fusion splice is considered the most reliable joint between two cables. This joint uses an electric arc to pass a high-voltage signal so that the maximum output is received at the end.
Difference between mechanical splicing and fusion splicing
S.No
Mechanical splicing
Fusion splicing
1
Mechanical splicing does not use any other thing to connect two cables.
Fusion splicing uses heat or an electric arc to join two cables.
2
Mechanical splicing holds two cables together using its own assembly.
Fusion splicing fuses two cables into one single cable
3
It is comparatively less expensive.
It’s more expensive than mechanical splicing.
4
Average signal loss is more because of variability in the type of connector used.
Average signal loss is less because they offer very high-quality signal transmission.
ConnectorFiber optics connectors are joints that are reusable, and easy to attach and detach at any point in time.
The connector is of two types −
DNP connector −
Dry No Polish connectors are pre-assembled connectors that do not require field polishing and assembling.
SMA connector −
It is a Sub Miniature type A coaxial connector that is used for high-frequency devices like a microwave, mobile signal antennae, wifi antennae, etc.
Difference between DNP and SMA connectorsS.no
DNP connector
SMA connector
1
DNP is Dry No Polish connector.
SMA is Sub Miniature type A connector.
2
It is a pre-assembled design.
It is a screw-type coupling design.
3
Installation is fast.
Installation is slower than the DNP connector.
CouplerIt is a device that divides one input signal into two output signals. Coupler can also be used for dividing two inputs into one output. In such cases, it is called a Combiner.
Different types of couplers are
T-Coupler −
The T-coupler is used split one incoming signal into two output signals using a grin lens and beam splitter.
Star Coupler −
The start coupler is used to split one incoming signal into many output signals.
Three ports coupler −
The three ports coupler splits one input signal into two output signals without using grin lens and beam splitter.
Difference between T-Coupler and Star coupler
S.no
T-Coupler
Star coupler
1
T-Coupler has one input and two outputs
A Star coupler has one input and many outputs.
2
The output power of the two ports is not evenly distributed.
The output power is equally distributed
3
It is used in bus types of networks and small networks.
It is used in large networks.
4
If anyone coupler in the network gets disconnected, all other terminals will also get disconnected.
If any one-star coupler terminal gets disconnected, it won’t impact other terminals in that network.
ConclusionMultiple types of Joints have been discussed in this article. The type of fiber optic joints to be used to connect two or more fiber optics cables depends on the following factors the joint should cause minimum power loss, it should be easy to install, it should be strong, and have less weight.
Learn The Latest Versions Of Pyspark
Introduction to PySpark version
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Versions of PySparkMany versions of PySpark have been released and are available to use for the general public. Some of the latest Spark versions supporting the Python language and having the major changes are given below :
1. Spark Release 2.3.0This is the fourth major release of the 2.x version of Apache Spark. This release includes a number of PySpark performance enhancements including the updates in DataSource and Data Streaming APIs.
Improvements were made regarding the performance and interoperability of python by vectorized execution and fast data serialization.
A new Spark History Server was added in order to provide better scalability for the large applications.
register* for UDFs in SQLContext and Catalog was deprecated in PySpark.
Python na.fill() function now also accepts boolean values and replaces the null values with booleans (in previous versions PySpark ignores it and returns the original DataFrame).
In order to respect session timezone, timestamp behavior was changed for the Panda related functionalities.
From this release, Pandas 0.19.2 or upper version is required for the user to use Panda related functionalities.
Many documentation changes and the test scripts were revised in this release for the Python language.
2. Spark Release 2.4.7This was basically the maintenance release including the bug fixes while maintaining the stability and security of the ongoing software system. Not any specific and major feature was introduced related to the Python API of PySpark in this release. Some of the notable changes that were made in this release are given below:
Now loading of the job UI page takes only 40 sec.
Python Scripts were changes that were failing in certain environments in previous releases.
Now users can compare two dataframes with the same schema (Except for the nullable property).
In the release DockerFile, R language version is upgraded to 4.0.2
Support for the R less than 3.5 version is dropped.
Exception messages at various places were improved.
Error messages were locked when failing in interpreter mode.
Many changes were made in the documentation for the inconsistent AWS variables.
3. Spark Release 3.0.0This is the first release of 3.x version. It brings many new ideas from the 2.x release and continues the same ongoing project in development. It was officially released in June 2023. The top component in this release is SparkSQL as more than 45% of the tickets were resolved on SparkSQL. It benefits all the high level APIs and high level libraries including the DataFrames and SQL. At this stage, Python is the most widely used language on Apache Spark. Millions of users downloaded Apache Spark with the Python language only. Major changes and the features that were introduced in this release are given below:
In this release functionality and usability is improved including the redesign of Pandas UDF APIs.
Various Pythonic error handling were done.
Python 2 support was deprecated in this release.
PySpark SQL exceptions were made more pythonic in this release.
Various changes in the test coverage and documentation of Python UDFs were made.
For K85 Python Bindings, Python 3 was made as the default language.
Validation sets were added to fit with Gradient Boosted trees in Python.
Parity was maintained in the ML function between Python and Scala programming language.
Various exceptions in the Python UDFs were improved as complaints by the Python users.
Now a multiclass logistic regression in PySpark correctly returns a LogisticRegressionSummary from this release.
4. Spark Release 3.0.1
Double catching was fixed in KMeans and BiKMeans.
Apache Arrow 1.0.0 was supported in SparkR.
For the overflow conditions, silent changes were made for timestamp parsing.
Revisiting keywords based on ANSI SQL standard was done.
Regression was done in handling the NaN values in Sql COUNT.
Changes were made for the Spark producing incorrect results in group by clause.
Grouping problems were resolved as per the case sensitivity in panda UDFs.
MLlibs acceleration docs were improved in this release.
Issues related to the LEFT JOIN found in the regression of 3.0.0 producing unexpected results were resolved.
5. Spark Release 3.1.1
Spark Release 3.1.1 would now be considered as the new official release of Apache Spark including the bug fixes and new features introduced in it. Though it was planned to be released in early January 2023, there is no official documentation of it available on its official site as of now.
ConclusionAbove description clearly explains the various versions of PySpark. Apache Spark is used widely in the IT industry. Python is a high level, general purpose and one of the most widely used languages. In order to implement the key features of Python in Spark framework and to use the building blocks of Spark with Python language, Python Spark (PySpark) is a precious gift of Apache Spark for the IT industry.
Recommended ArticlesThis is a guide to PySpark version. Here we discuss Some of the latest Spark versions supporting the Python language and having the major changes. You may also have a look at the following articles to learn more –
Learn The Example Of Opencv Puttext
Introduction to OpenCV putText()
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It is also needed that the starting point for the text has to be defined within the matrix. there is also a requirement for defining the font color for the text, the font style for the text, and the weight that the text has two be specified with. The function is present in the OpenCV library of Python programming language, which is a one-stop solution that has been designed in order to solve problems related to computer vision.
Syntax for OpenCV putText()
cv2.put Text (* image *, text *, org *, font *, fontScale *, color [*, thickness [,line Type [*,* bottom Left Origin *] *] *] *) * Parameters for OpenCV put text functionThe following parameters are accepted by the OpenCV putText() function:
Parameters Description of the parameters:
image this parameter represents the original image that the user has selected to add text by the system
text This parameter represents the text that has to be drawn by the system as specified by the user
org This parameter is used to represent the coordinate with respect to the text present on the bottom left corner of the image. These coordinates are represented with the help of 2 double values that are passed, which represent the X coordinate and the Y coordinate values, respectively
font This parameter is used to represent the type or style of font, which would be denoted for the string text that the user specifies. some instances for the kinds of font types that can be used are FONT * _ * HERSHEY * _ * PLAIN OR FONT * _ * HERSHEY * _ * SIMPLEX
font * scale This parameter represents the best size for the specified font size, which is relevant to the font scale factor, which acts as a multiplying factor further font size of the text that has to be entered
thickness this parameter represents the thickness that has to be given for the line of text that has to be entered by the user. it is measured in terms of pixel size
color this parameter represents the specific color that has to be given to the text string that is being entered into the image that is being drawn on the screen. The color is extracted from the BGR tuple, which is passed to it. for instance, for a text of blue color the tuple to be passed would be * (* 255 *, * 0 *, * 0) *
Line * Type This parameter is used to define the type of line used for the text, which has to be entered into the image. This parameter is an optional parameter.
Bottom * Left * Origin this parameter is used for defining the position for the image data origin with respect to the directional position in the image. this parameter is an optional parameter. If the parameter is taken as true, the image data origin is found to be placed at the bottom left corner of the image. If it is not true, the image data origin is placed at the top left corner of the image.
Return * Value This method is responsible for returning an output image that is to be loaded from the file which has been specified.
Example of OpenCV putText()Following is the example which is used in order to demonstrate how the OpenCV putText() command is utilized in the Python programming language
# command used to import the OpenCV library to utilize OpenCV read image function import cv2 # path being defined from where the system will read the image path = r'C:Users Priyanka Desktop educba OpenCV edu cba logo.png' # command used for reading an image from the disk disk, cv2.imread function is used image1 = cv2.imread(path) # Window name being specified where the image will be displayed window_name1 = 'image' # font for the text being specified font1 = cv2.FONT_HERSHEY_SIMPLEX # org for the text being specified org1 = (50, 50) # font scale for the text being specified fontScale1 = 1 # Blue color for the text being specified from BGR color1 = ( 255 , 0 , 0 ) # Line thickness for the text being specified at 2 px thickness1 = 2 # Using the cv2.putText() method for inserting text in the image of the specified path image_1 = cv2.putText(image1, 'EDU CBA', org1, font1, fontScale1, color1, thickness1, cv2.LINE_AA) # Displaying the output image cv2.imshow(window_name, image_1) cv2.waitKey(0) cv2.destroyAllWindows() ConclusionThe OpenCV putText() method is a very useful function present in the OpenCV library, which allows the system to add text to an image that the user has provided. There are several image processing areas where text needs to be associated with the images that are being processed, and there needs to be a variety in the color, font style, width, and orientation in terms of the position whether the text has to be placed on the image which can easily be utilized by using the put text method. It also reduces the verbosity of the program that is being written and increases the overall processing speed for the program to be executed.
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