TCP简单实现

服务器端：
1.socket创建一个嵌套字
2.bind绑定一个地址到嵌套字
3.listen接受链接请求
4.accept链接请求并建立链接

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/un.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>

#define SERVERPATH "/tmp/server"

int processConnect(int newsd,int sd)
{
    pid_t pid=fork();
    if(pid==-1)
    {
        perror("fork");
        exit(-1);
    }
    if(pid==0)
    {
        close(sd);
        char buf[100];
        int fd,ret;

        fd=open("/etc/passwd",O_RDONLY);
        if(fd==-1)
        {
            perror("open");
            exit(-1);
        }
        while(1)
        {
            ret=read(fd,buf,100);
            if(ret==-1)
            {
                perror("read");
                return -1;
            }
            if(ret==0)
            {
                break;
            }
            write(newsd,buf,ret);
        }
        close(newsd);
        close(fd);
        exit(0);
    }
    return 0;
}

int main(void)
{
    int sd,newsd,ret;
    struct sockaddr_un addr;
    socklen_t length;

    addr.sun_family=AF_UNIX;
    strncpy(addr.sun_path,SERVERPATH,108);
    length=sizeof(addr);

    sd=socket(AF_UNIX,SOCK_STREAM,0);
    if(sd==-1)
    {
        perror("socket");
        exit(-1);
    }

    unlink(SERVERPATH);

    ret = bind(sd,(struct sockaddr *)&addr,length);
    if(ret==-1)
    {
        perror("bind");
        exit(-1);
    }
    ret=listen(sd,10);
    if(ret==-1)
    {
        perror("listen");
        exit(-1);
    }
    while(1)
    {
        newsd=accept(sd,NULL,NULL);
        if(newsd==-1)
        {
            perror("accept");
            exit(-1);
        }
        ret=processConnect(newsd,sd);
        if(ret==-1)
        {
            close(sd);
            close(newsd);
            exit(-1);
        }
        close(newsd);
    }
    close(sd);
    exit(0);
}

客户端：
1.socket创建一个嵌套字
2.connect链接到服务器

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <string.h>

#define SERVERPATH "/tmp/server"

int main(void)
{
    int sd,newsd,ret;
    struct sockaddr_un addr;
    socklen_t length;
    char buf[100];

    addr.sun_family=AF_UNIX;
    strncpy(addr.sun_path,SERVERPATH,108);
    length=sizeof(addr);

    sd=socket(AF_UNIX,SOCK_STREAM,0);
    if(sd==-1)
    {
        perror("socket");
        exit(-1);
    }
    ret = connect(sd,(struct sockaddr *)&addr,length);
    if(ret==-1)
    {
        perror("connect");
        exit(-1);
    }

    while(1)
    {
        ret=read(sd,buf,100);
        if(ret==-1)
        {
            perror("read");
            exit(-1);
        }
        if(ret==0)
        {
            break;
        }
        write(1,buf,ret);
    }
    close(sd);
    exit(0);
}