C TCP Server in Windows – Thread per connection2 min read

A simple TCP server in C (windows). It works in a “thread per connection” way.

Note- I don’t know what I am doing.

#include <winsock.h> 
#include <stdio.h> 
#include <string.h> 
#include <sys/types.h>

#define PORT 50001

//Function that threads run
static DWORD __stdcall func(int s);

int main() {
  //Dont ask just put it in there
  WSADATA wsaData;
  if (WSAStartup(MAKEWORD(2, 0), & wsaData) != 0) {
    fprintf(stderr, "WSAStartup failed.\n");
    exit(1);
  }

  //Socket initiation
  int sock;
  if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) {
    printf("Socket initiation failed!");
    return 0;
  }

  //Socket settings
  struct sockaddr_in addr;
  addr.sin_family = AF_INET;
  addr.sin_port = htons(PORT);
  addr.sin_addr.s_addr = inet_addr("127.0.0.1");
  memset(addr.sin_zero, '\0', sizeof addr.sin_zero);

  //Bind the socket
  int b;
  if ((b = bind(sock, & addr, sizeof(addr))) == SOCKET_ERROR) {
    printf("Socket initiation failed!");
    return 0;
  }

  //Listen on socket
  int l = listen(sock, 25);

  printf("TCP server listening on port %d\n", PORT);

  //If (con) pass it to a new thread 
  while (1) {
    struct sockaddr_in client_addr;
    unsigned int c_len = sizeof client_addr;
    int s1 = accept(sock, & client_addr, & c_len);
    unsigned int cur_tid;

    _beginthreadex(NULL, 0, func, s1, 0, & cur_tid);
  }

  //Cleanup
  closesocket(sock);
  WSACleanup();
  return 0;
}

static DWORD __stdcall func(int s) {
  puts("Connection accepted");

  //Read data from client
  char buff[1024];
  unsigned int tot_bytes = recv(s, buff, sizeof(buff), MSG_PEEK);
  char * client_data = (char * ) malloc(tot_bytes + 1);
  for (int i = 0; i < (tot_bytes); i++) {
    client_data[i] = buff[i];
  }
  client_data[tot_bytes] = '\0';

  printf("Msg from client: %s\n", client_data);

  //Pretend you are processing info
  puts("Processing req");
  Sleep(5000);
  puts("Processing complete");

  //Prepare message for the client
  char * message;
  if (strcmp(client_data, "COMMAND1") == 0) {
    char lmsg[] = "COMMAND1 recieved";
    message = (char * ) malloc(strlen(lmsg));
    message = lmsg;
  } else if (strcmp(client_data, "COMMAND2") == 0) {
    char lmsg[] = "COMMAND2 recieved";
    message = (char * ) malloc(strlen(lmsg));
    message = lmsg;
  } else {
    char lmsg[] = "NO COMMAND recieved";
    message = (char * ) malloc(strlen(lmsg));
    message = lmsg;
  }

  free(client_data);

  //Send data to client
  send(s, message, strlen(message), 0);

  return 0;
}

TCP client in Node.js

var net = require('net');

var client1 = new net.Socket();
client1.connect(50001, '127.0.0.1', function() {
  console.log('Connected');
  client1.write('COMMAND1');
});

client1.on('data', function(data) {
  console.log('Received on 1: ' + data);
  client1.destroy();
});

client1.on('close', function() {
  console.log('Connection closed on 1');
});

var client2 = new net.Socket();
client2.connect(50001, '127.0.0.1', function() {
  console.log('Connected on 2');
  client2.write('COMMAND2');
});

client2.on('data', function(data) {
  console.log('Received on 2: ' + data);
  client2.destroy();
});

client2.on('close', function() {
  console.log('Connection closed on 2');
});

See single threaded windows TCP server using IO Completion Ports – https://github.com/hrishimk/iocp_tcp_server