C学习 - Linux下的Tcp Server

#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define SERVER_PORT_NUM      50001
#define MAX_DATA_BUFSIZE     6000
#define ERROR                -1
#define OK                   0

unsigned char buf[MAX_DATA_BUFSIZE] = {0};

/* Function declaration  */
int main()
{
    struct sockaddr_in serverAddr;
    struct sockaddr_in clientAddr;
    int    sockAddrSize;
    int    accept_fd;
    int    sock_fd;
    fd_set fdset;
    int    bytes_received = 0;
    int    seq = 0;
    int    pkt_len = 0;

    sockAddrSize = sizeof(struct sockaddr_in);

    bzero((char*) &serverAddr, sockAddrSize);
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port   = htons(SERVER_PORT_NUM);
    serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);

    if ((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) == ERROR)
    {
        printf("Error: socket()!\n");
        return ERROR;
    }

    if (bind(sock_fd, (struct sockaddr *) &serverAddr, sizeof(serverAddr)) == ERROR)
    {
        printf("Error: bind()!\n");
        close(sock_fd);
        return ERROR;
    }

    while (1)
    {
        if ((bytes_received = recvfrom(sock_fd, buf, MAX_DATA_BUFSIZE, 0, (struct sockaddr *) &clientAddr, &sockAddrSize)) > 0)
        {
            /* Print the contents of the received msg, the first 4 bytes is seq num */
            seq = (buf[0]<<24) + (buf[1]<<16) + (buf[2]<<8) + buf[3];
            printf("Received %4d bytes Data. seq=%d \n", bytes_received, seq);
        }
    }

    close(sock_fd);

    return OK;
}