#include <stdio.h>
#include <wireshark/epan/packet.h>
#include <wireshark/epan/prefs.h>

// Define protocol IDs
static int proto_my_protocol = -1;
static dissector_handle_t my_protocol_handle;

// Define fields
static int hf_my_protocol_field1 = -1;
static int hf_my_protocol_field2 = -1;

// Define the protocol subtree
static gint ett_my_protocol = -1;

void dissect_my_protocol(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
    proto_item *ti = NULL;
    proto_tree *my_protocol_tree = NULL;

    // Add the protocol to the tree
    ti = proto_tree_add_item(tree, proto_my_protocol, tvb, 0, -1, ENC_NA);
    my_protocol_tree = proto_item_add_subtree(ti, ett_my_protocol);

    // Add fields to the protocol tree
    proto_tree_add_item(my_protocol_tree, hf_my_protocol_field1, tvb, 0, 1, ENC_BIG_ENDIAN);
    proto_tree_add_item(my_protocol_tree, hf_my_protocol_field2, tvb, 1, 2, ENC_BIG_ENDIAN);
}

void proto_register_my_protocol(void) {
    // Register the protocol
    static hf_register_info hf[] = {
        { &hf_my_protocol_field1,
          { "Field 1", "my_protocol.field1", FT_UINT8, BASE_HEX, NULL, 0x0, NULL, HFILL }},
        { &hf_my_protocol_field2,
          { "Field 2", "my_protocol.field2", FT_UINT16, BASE_HEX, NULL, 0x0, NULL, HFILL }},
    };

    // Register the protocol subtree
    static gint *ett[] = {
        &ett_my_protocol,
    };

    // Register the protocol
    proto_my_protocol = proto_register_protocol("My Protocol", "My Protocol", "my_protocol");
    proto_register_field_array(proto_my_protocol, hf, array_length(hf));
    proto_register_subtree_array(ett, array_length(ett));

    // Register the dissector
    my_protocol_handle = create_dissector_handle(dissect_my_protocol, proto_my_protocol);
    register_dissector("my_protocol", dissect_my_protocol, my_protocol_handle);
}

void proto_reg_handoff_my_protocol(void) {
    // Register the dissector
    dissector_add("udp.port", my_protocol_handle);
}

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Read inputs from stdin

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#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}