UNIX 回射程序

必需感慨一下，網絡程序的細節真的是太多了，任何一個步驟都有可能出現問題！而且還要處理所遇到的問題！！！

服務器：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>


#define SERV_PORT    9978
#define LISTENQ   5
#define MAXLINE   4096

typedef struct sockaddr SA;

int
main(int argc, char *agrv[])
{
    void str_echo(int sockfd) ;
    int listenfd, connfd;
    pid_t childpid;
    socklen_t  clilen;
    struct sockaddr_in cliaddr, servaddr;

    listenfd = socket(AF_INET, SOCK_STREAM, 0);  // maybe have errror

    memset(&servaddr, 0, 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));   // maybe have error

    listen(listenfd, LISTENQ);   // maybe have error

    for (;;) {
        clilen = sizeof(cliaddr);
        connfd = accept(listenfd, (SA *)&cliaddr, &clilen);   // maybe have error
        if ((childpid = fork()) == 0) {    // maybe have error
            close(listenfd);

            str_echo(connfd); // deal connfd


            // close(connfd);   // unnecessary statement
            exit(0);
        }
        close(connfd);    // maybe have error
    }

    return 0;
}

void 
str_echo(int sockfd)
{
    ssize_t n;
    char buf[MAXLINE];

    do {
        while ( (n=read(sockfd, buf, MAXLINE)) >0)
            write(sockfd, buf, n);
    } while (n<0 && errno==EINTR);

    if (n<0) {
        perror("str_echo:read error");
        exit(1);
    }
}

客戶端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define SERV_PORT    9978
#define LISTENQ   5
#define MAXLINE   4096

typedef struct sockaddr SA;

int
main(int argc, char *argv[])
{
    void str_cli(FILE *fp, int sockfd);

    int sockfd;
    struct sockaddr_in servaddr;

    if (argc != 2) {
        perror("usage: tcpcli <IPaddress>");
        exit(-1);
    }

    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    memset(&sockfd, 0, sizeof(sockfd));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(SERV_PORT);
    inet_pton(AF_INET, argv[1], &servaddr.sin_addr);

    connect(sockfd, (SA *)&servaddr, sizeof(servaddr));

    str_cli(stdin, sockfd);

    exit(0);
    return 0;
}

void
str_cli(FILE *fp, int sockfd)
{
    char sendline[MAXLINE], recvline[MAXLINE];
    while (fgets(sendline, MAXLINE, fp) != NULL) {
        write(sockfd, sendline, strlen(sendline));
        if (read(sockfd, recvline, MAXLINE) == 0) {
            perror("str_cli: server teminated prematurely");
        }
        fputs(recvline, stdout);
    }
}