简单socket程序

1，int   socket(int domain,int type,int protocol)  

domain :

AF_INET   ipv4

AF_UNIX 进程间通信的一种方式，命名socket特殊的，不走ip层

type：

SOCKET_DGRAM UDP报文

SOCK_STREAM  TCP报文

protocol: 

IPPROTO_ICMP：ping命令实现报文

IPPROTO_TCP ,IPPRO_UDP

常用 listen_fd 作为返回值

2，bind()

int bind(int sock_fd, const struct sockaddr *addr, socklen_t addrlen)

sock_fd :socket返回的文件描述符

addr :绑定的ip地址和端口信息

addrlen :addr 长度

serv_addr.sin_family = AF_STREAM

serv_addr.sin_port = htons(8889)  host to net  short类型 大端字节数

serv_addr.sin_addr.s_addr = htonl("xxxxxxx")  long      绑定ip地址  

头文件： #include <netinet/in.h>
           #include <arpa/inet.h>

3，listen()  

int listen(int sock_fd,int backlog) backlog 有多少客户端

4，accept()

int accept(int sock_fd,struct sockaddr *addr,socklen_t *addrlen)  //套路

addr 和 addrlen 一般是NULL 分别是客户端的IP和端口信息

返回的fd给客户端通信

5，connect()

int connect(int sockfd, const struct sockaddr *addr,
                   socklen_t addrlen);

 如 ：connect(conn_fd,(const struct sockaddr *)&serv_addr,sizeof(serv_addr)

客户端程序：

注：

客户端

inet_aton("127.0.0.1",)

回环设备不走网络层，

服务器程序：

/*********************************************************************************
 *      Copyright:  (C) 2018 ligang<2820724771@qq.com>
 *                  All rights reserved.
 *
 *       Filename:  socket_server.c
 *    Description:  This file 
 *                 
 *        Version:  1.0.0(03/16/2018)
 *         Author:  ligang <2820724771@qq.com>
 *      ChangeLog:  1, Release initial version on "03/16/2018 10:24:16 PM"
 *                 
 ********************************************************************************/

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

int main(int argc,char **argv)
{
    int sock_fd,new_fd;
    struct sockaddr_in serv_addr;
    char buf[1024];

    sock_fd = socket(AF_INET,SOCK_STREAM,0);
    if(sock_fd < 0)
    {
       printf("create socket is failure %s\n",strerror(errno));
        return -1;
    }

    printf("create socket fd [%d]\n",sock_fd);

    memset(&serv_addr, 0, sizeof(struct sockaddr_in));
    printf("memset\n");
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(8555);
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);

        printf("begin to bind\n");

    if(bind(sock_fd,(const struct sockaddr *)&serv_addr,sizeof(serv_addr))<0)
    {

        printf("bind is failure %s\n ",strerror(errno));
        return -2;
    }

        printf("begin to listen\n");
    listen(sock_fd,13);

    while(1)
    {
        printf("begin to accepting!\n");
        new_fd = accept(sock_fd,NULL,NULL);
        if(new_fd<0)
        {
            printf("accept is failure %s\n",strerror(errno));
            return -2;
        }
        memset(buf,0,sizeof(buf));
        read(new_fd,buf,sizeof(buf));
        printf("read message is %s\n",buf);

        write(new_fd,"welcome",7);
        sleep(1);
        close(new_fd);
    
    }

    close(sock_fd);
    return 0;
}



客户端程序：

[ligang@MiWiFi-R3P-srv ~]$ cat my_socket_client.c 
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main(int argc,char **argv)
{
        int conn_fd;
        struct sockaddr_in serv_addr;
        char buf[1024];

        conn_fd=socket(AF_INET,SOCK_STREAM,0);
        if(conn_fd<0)
        {
                printf("create socket is failure %s\n",strerror(errno));
                return -1;
        }
        printf("create socket number [%d]\n",conn_fd);

        memset(&serv_addr,0,sizeof(serv_addr));
        serv_addr.sin_family = AF_INET;
        serv_addr.sin_port = htons(8555);
        if(inet_pton(AF_INET,argv[1],&serv_addr.sin_addr)==0)
    {
        printf("ip addr is failure:%s\n",strerror(errno));
        return -1;
    }

        printf("begin to connecting\n");

        if(connect(conn_fd,(const struct sockaddr *)&serv_addr,sizeof(serv_addr))==-1)
        {
          printf("connect is failuren  %s\n",strerror(errno));
          return -2;
        }

        printf("connect is sucess\n");

        write(conn_fd,"hello",5);

        memset(buf,0,sizeof(buf));
        read(conn_fd,buf,sizeof(buf));
        printf("receive : %s\n ",buf);

        close(conn_fd);
        return 0;


}

[ligang@MiWiFi-R3P-srv ~]$ gcc my_socket_server.c
[ligang@MiWiFi-R3P-srv ~]$ ./a.out
create socket fd [3]
memset
begin to bind
begin to listen
begin to accepting!
read message is hello
begin to accepting!
^C

[ligang@MiWiFi-R3P-srv ~]$ gcc my_socket_client.c
[ligang@MiWiFi-R3P-srv ~]$ ./a.out 192.168.0.139
create socket number [3]
begin to connecting
connect is sucess
receive : welcome

输入错误服务地址：
 [ligang@MiWiFi-R3P-srv ~]$ ./a.out  192.168.0.1
create socket number [3]
begin to connecting
connect is failuren  Connection refused