UNP——TCP分析

tcpserver.c

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <time.h>
#include <arpa/inet.h>
#include "proto.h"

#define bakc_log 50
#define praddr_size 50
#define buffer_size 1024
static void server_job(int sockfd)
{
    int len;
    char buffer[buffer_size];
    len = sprintf(buffer,FMT_STAMP, (long long)time(NULL));

    if(send(sockfd, buffer, len, 0)<0)
    {
        perror("send");
        exit(1);
    }
}

int main()
{
    int sd,std;
    int flag;
    pid_t pid;
    char p_raddr[praddr_size];
    struct sockaddr_in laddr,raddr;
    laddr.sin_family = AF_INET;
    laddr.sin_port = htons(LOCALPORT);
    inet_pton(AF_INET,"0.0.0.0",&laddr.sin_addr);

    socklen_t laddrsize = sizeof(laddr);
    socklen_t raddrsize = sizeof(raddr);
    sd = socket(AF_INET,SOCK_STREAM,0);
    if(sd<0)
    {
        perror("socket");
        exit(1);
    }

    if(setsockopt(sd,SOL_SOCKET,SO_REUSEADDR,&flag,sizeof(flag))<0)
    {
        perror("setsocket");
        exit(1);
    }

    if(bind(sd, (void*)&laddr, laddrsize)<0)
    {
        perror("bind");
        exit(1);
    }

    if(listen(sd,bakc_log)<0)
    {
        perror("listen");
        exit(1);
    }

    while(1)
    {
            //accept返回三個值，std即可能是已連接套接字或錯誤信息，對端地址，對端地址大小
        std = accept(sd, (void*)&raddr,&raddrsize);  //返回值爲全新文件描述符，代表與tcp對端連接，已連接描述符
        if(std < 0)
        {
            perror("accept");
            exit(1);
        }
        pid = fork();  //併發的時候，應該注意：fork之後，子進程和父進程均有已連接描述符和監聽描述符，父進程中需close已連接描述符
                        //，將引用計數減爲0
        if(pid == 0)
        {
            close(sd);
            inet_ntop(AF_INET,&raddr.sin_addr,p_raddr,praddr_size);
            fprintf(stderr,"Client addr is %s , port is %d\n",p_raddr,ntohs(raddr.sin_port));

            server_job(std);
            close(std);
            exit(0); //子進程結束必須exit0，否則會繼續執行
        }
        close(std); //此處必須有，計數減爲0，然後纔會發送FIN，四次分手
    }

    close(sd);
    exit(0);
}

tcpclient.c

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include "proto.h"
#define raddr_size 40
int main(int argc, char* argv[])
{

    FILE* fp;
    long long stamp;
    struct sockaddr_in laddr,raddr;
    char raddr_ip[raddr_size];
    if(argc < 2)
    {
        fprintf(stderr,"argc");
        exit(1);
    }

    int sd = socket(AF_INET,SOCK_STREAM,0);
    if(sd<0)
    {
        perror("socket");
        exit(1);
    }
    raddr.sin_family = AF_INET;
    raddr.sin_port = htons(LOCALPORT);
    inet_pton(AF_INET,argv[1],&raddr.sin_addr);
    fprintf(stderr,"let's go");
    if(connect(sd,(void*)&raddr,sizeof(raddr))<0)  //conncet開始三次握手，可能出現三種情況1、FIN無ACK，75s後ETIMEOUT
    {
        perror("connect");
        exit(1);
    }

    //一切皆文件
    fp = fdopen(sd,"r+"); //將文件描述符轉換成FILE指針打開,這裏不能用w，w+，因無需創建fd

    if(fp==NULL)
    {
        perror("fdopen");
        exit(1);
    }

    if(fscanf(fp,FMT_STAMP,&stamp)<1) //返回成功讀取的個數，這裏只有一個item，正確爲1
    {

        fprintf(stderr,"error FMT_STAMP");
    }
    else
    {
        fprintf(stderr,"stamp = %lld\n",stamp);
    }

    fclose(fp); //這裏需要關閉fp，因爲fdopen已經轉成fp

    exit(0);
}

proto.h

#ifndef PROTO_H__
#define PROTO_H__

#define LOCALPORT 1990
#define FMT_STAMP "%lld\r\n"


#endif