multi-process tcp echo server

server.c

#ifdef _win32_
#include <winsock2.h>
#else
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <strings.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <errno.h>
#endif

#define SERV_PORT 7777
#define LISTENQ     1024
#define SA struct sockaddr
#define BUF_SIZE 1024

static char buffer[BUF_SIZE];

void
send_buf(int fd, size_t len)
{
    size_t count = 0, t;
    while ((((t = write(fd, buffer, len - count)) >= 0) || errno == EINTR)
            && (count != len)) {
        count += t > 0 ? t : 0;
    }
}

void
str_echo(int fd)
{
    size_t t;
    for ( ; ; ) {
        t = read(fd, buffer, sizeof(buffer));
        if (t > 0) {
            send_buf(fd, t);
        } else if (t == 0) { // 0 => EOF
            break;
        } else if (t < 0) {
            if (errno != EINTR) {
                break;
            } else
                continue;
        }
    }
}

int
main(int argc, char *argv[])
{
    int listenfd, connfd;
    pid_t childpid;
    socklen_t chilen;
    struct sockaddr_in cliaddr, servaddr;

    listenfd = socket(AF_INET,  SOCK_STREAM, 0);
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);

    bind(listenfd, (SA*) &servaddr, sizeof(servaddr));
    listen(listenfd, LISTENQ);

    for (; ;) {
        chilen = sizeof(cliaddr);
        connfd = accept(listenfd, (SA*) &cliaddr, &chilen);

        if ( (childpid =  fork()) == 0) {
            close(listenfd);
            str_echo(connfd);
            exit(0);
        }
        close(connfd);
    }
}