Linux_ マルチプロセス同時サービスTCP

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <signal.h>

#define BUFF_SIZE 1024


int main(void)
{
    int sockfd;
    struct sockaddr_in server_addr, client_addr;
    int ret;
    int pd;
    char buff[BUFF_SIZE];

    sockfd = socket (AF_INET, SOCK_STREAM, 0);
    server_addr.sin_addr.s_addr = inet_addr("10.10.0.9");
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(9000);


    ret = connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));
    if (ret == -1) {
        perror("connect");
        exit(errno);
    }

    sprintf(buff, "process(%u) send msg", getpid());
    ret = write(sockfd, buff, strlen(buff)+1);
    if (ret == -1) {
        perror("client write");
        exit(errno);
    }

    ret = read(sockfd, buff, sizeof(buff));
    if (ret == -1) {
        perror("client read");
        exit(errno);
    }

    printf("received: %s
", buff);

    exit(0);
}

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <signal.h>

#define BUFF_SIZE 1024

void handle_sigchld(int sig)
{
    printf("catch a sig(%d)
", sig);
    wait(NULL);
}

static void str2up(char *p)
{
    while (*p) {
        if (*p >= 'a' && *p <= 'z') {
            *p = *p - 'a' + 'A';
        }
        p++;
    }
}

int main(void)
{
    int sockfd, clientfd;
    struct sockaddr_in server_addr, client_addr;
    int ret;
    int pd;
    char buff[BUFF_SIZE];
    //socklen_t len = sizeof(struct sockaddr_in);
    socklen_t len= sizeof(struct sockaddr);

    sockfd = socket (AF_INET, SOCK_STREAM, 0);
    server_addr.sin_addr.s_addr = htons(INADDR_ANY);
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(9000);

    ret = bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));
    if (ret == -1) {
        perror("bind");
        exit(errno);
    }

    ret = listen(sockfd, 5);
    if (ret == -1) {
        perror("listen");
        exit(errno);
    }

    signal(SIGCHLD, handle_sigchld);

    while (1) {
        clientfd = accept(sockfd, (struct sockaddr*)&server_addr, &len);
        if (clientfd == -1) {
            perror("accept");
            exit(errno);
        }
        printf("clientfd=%d
", clientfd);
        pd = fork();
        if (pd == -1) {
            perror("fork");
            exit(errno);
        } else if (pd == 0) {
            close(sockfd);

            ret = read(clientfd, buff, sizeof(buff));
            printf("Process(%d),ret=%d, received: %s
", getpid(), ret, buff);

            str2up(buff);

            ret = write(clientfd, buff, strlen(buff)+1);
            printf("ret=%d
", ret);

            close(clientfd);            
            exit(0);
        } 


    }

    exit(0);
}