To build a TCP server in C++, you can follow these steps:

1. Create a socket using the socket() function. Specify the address family, socket type, and protocol.

   TEXT/X-C++SRC

   1int sockfd = socket(AF_INET, SOCK_STREAM, 0);
   2if (sockfd == -1) {
   3  std::cout << "Failed to create socket" << std::endl;
   4  return 1;
   5}

2. Bind the socket to an address and port using the bind() function. Specify the server address and port in a sockaddr_in structure.

   TEXT/X-C++SRC

   1struct sockaddr_in serverAddr;
   2serverAddr.sin_family = AF_INET;
   3serverAddr.sin_port = htons(8080);
   4serverAddr.sin_addr.s_addr = INADDR_ANY;
   5
   6if (bind(sockfd, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) == -1) {
   7  std::cout << "Failed to bind socket" << std::endl;
   8  return 1;
   9}

3. Listen for incoming connections using the listen() function. Specify the maximum number of queued connections.

   TEXT/X-C++SRC

   1if (listen(sockfd, 5) == -1) {
   2  std::cout << "Failed to listen for connections" << std::endl;
   3  return 1;
   4}

4. Accept incoming connections using the accept() function. Specify a sockaddr_in structure to store the client address.

   TEXT/X-C++SRC

   1struct sockaddr_in clientAddr;
   2unsigned int clientAddrSize = sizeof(clientAddr);
   3int clientSock = accept(sockfd, (struct sockaddr*)&clientAddr, &clientAddrSize);
   4if (clientSock == -1) {
   5  std::cout << "Failed to accept connection" << std::endl;
   6  return 1;
   7}

5. Send and receive data on the client socket using the read() and write() functions.

   TEXT/X-C++SRC

   1char buffer[1024] = {0};
   2read(clientSock, buffer, 1024);
   3std::cout << "Received message: " << buffer << std::endl;
   4
   5const char* response = "Hello from the server!";
   6write(clientSock, response, strlen(response));

6. Close the client socket and server socket using the close() function.

   TEXT/X-C++SRC

   1close(clientSock);
   2close(sockfd);

Here's an example code that demonstrates how to build a TCP server in C++:

1#include <iostream>
2#include <sys/socket.h>
3#include <netinet/in.h>
4#include <unistd.h>
5
6int main() {
7  // Create a socket
8  int sockfd = socket(AF_INET, SOCK_STREAM, 0);
9  if (sockfd == -1) {
10    std::cout << "Failed to create socket" << std::endl;
11    return 1;
12  }
13
14  // Bind the socket to an address and port
15  struct sockaddr_in serverAddr;
16  serverAddr.sin_family = AF_INET;
17  serverAddr.sin_port = htons(8080);
18  serverAddr.sin_addr.s_addr = INADDR_ANY;
19
20  if (bind(sockfd, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) == -1) {
21    std::cout << "Failed to bind socket" << std::endl;
22    return 1;
23  }
24
25  // Listen for incoming connections
26  if (listen(sockfd, 5) == -1) {
27    std::cout << "Failed to listen for connections" << std::endl;
28    return 1;
29  }
30
31  // Accept incoming connections
32  struct sockaddr_in clientAddr;
33  unsigned int clientAddrSize = sizeof(clientAddr);
34  int clientSock = accept(sockfd, (struct sockaddr*)&clientAddr, &clientAddrSize);
35  if (clientSock == -1) {
36    std::cout << "Failed to accept connection" << std::endl;
37    return 1;
38  }
39
40  // Send and receive data on the client socket
41  char buffer[1024] = {0};
42  read(clientSock, buffer, 1024);
43  std::cout << "Received message: " << buffer << std::endl;
44
45  const char* response = "Hello from the server!";
46  write(clientSock, response, strlen(response));
47
48  // Close the client socket
49  close(clientSock);
50
51  // Close the server socket
52  close(sockfd);
53
54  return 0;
55}

xxxxxxxxxx

}

#include <iostream>

#include <sys/socket.h>

#include <netinet/in.h>

#include <unistd.h>

​

double calculate_interest(double principal, double rate, int years) {

  return principal * rate * years;

}

​

int main() {

  // Create a socket

  int sockfd = socket(AF_INET, SOCK_STREAM, 0);

  if (sockfd == -1) {

    std::cout << "Failed to create socket" << std::endl;

    return 1;

  }

​

  // Bind the socket to an address and port

  struct sockaddr_in serverAddr;

  serverAddr.sin_family = AF_INET;

  serverAddr.sin_port = htons(8080);

  serverAddr.sin_addr.s_addr = INADDR_ANY;

​

  if (bind(sockfd, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) == -1) {

    std::cout << "Failed to bind socket" << std::endl;

    return 1;

  }

​

  // Listen for incoming connections