网络编程--接口函数

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

#define SERVER_PORT 5555 
#define MAXLINE 4096
int main(void)
{
    struct sockaddr_in serveraddr, clientaddr;
    int sockfd, addrlen, confd, len, i;
    char ipstr[128];
    char buf[MAXLINE];

    //1.socket
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    //2.bind
    bzero(&serveraddr, sizeof(serveraddr));
    /* 地址族协议IPv4 */
    serveraddr.sin_family = AF_INET;
    /* IP地址 */
    serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
    serveraddr.sin_port = htons(SERVER_PORT);
    bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));
    //3.listen
    listen(sockfd, 128);
    while (1) {
        //4.accept阻塞监听客户端链接请求
        addrlen = sizeof(clientaddr);
        confd = accept(sockfd, (struct sockaddr *)&clientaddr, &addrlen);
        //输出客户端IP地址和端口号
        printf("client ip %s\tport %d\n", 
                inet_ntop(AF_INET, &clientaddr.sin_addr.s_addr, ipstr, sizeof(ipstr)),
                ntohs(clientaddr.sin_port));

        //和客户端交互数据操作confd
        //5.处理客户端请求 
        len = read(confd, buf, sizeof(buf));
        i = 0;
        while (i < len) {
            buf[i] = toupper(buf[i]);
            i++;
        }
        write(confd, buf, len);

        close(confd);
    }
    close(sockfd);

    return 0;
}

#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#define SERVER_PORT 8000
#define MAXLINE 4096
int main(int argc, char *argv[])
{
    struct sockaddr_in serveraddr;
    int confd, len;
    char ipstr[] = "192.168.6.254";
    char buf[MAXLINE];
    if (argc < 2) {
        printf("./client str\n");
        exit(1);
    }
    //1.创建一个socket
    confd = socket(AF_INET, SOCK_STREAM, 0);
    //2.初始化服务器地址
    bzero(&serveraddr, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    //"192.168.6.254"
    inet_pton(AF_INET, ipstr, &serveraddr.sin_addr.s_addr);
    serveraddr.sin_port  = htons(SERVER_PORT);
    //3.链接服务器
    connect(confd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));

    //4.请求服务器处理数据
    write(confd, argv[1], strlen(argv[1]));
    len = read(confd, buf, sizeof(buf));
    write(STDOUT_FILENO, buf, len);

    //5.关闭socket
    close(confd);
    return 0;
}

all:server client


server:server.c
    gcc $< -o $@

client:client.c
    gcc $< -o $@


.PHONY:clean
clean:
    rm -f server
    rm -f client

#include <sys/socket.h>
ssize_t recvfrom(int sockfd, void *buff, size_t nbytes, int flags, struct sockaddr *from, socklen_t *addrlen); 
ssize_t sendto(int sockfd, const void *buff, size_t nbytes, int flags, const struct sockaddr *to, socklen_t addrlen);
//均返回：若成功则为读或写的字节数，出错为-1
默认情况recvfrom函数没有接收到对方数据时候是阻塞的

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

#define SERVER_PORT 5556 
#define MAXLINE 1024 
int main(void)
{
    int sockfd,i;
    ssize_t len;
    struct sockaddr_in serveraddr,clientaddr;
    char buf[MAXLINE];
    char ipstr[INET_ADDRSTRLEN];//16个字节
    socklen_t clientlen;

    //构造用于UDP通信的套接字
    sockfd=socket(AF_INET,SOCK_DGRAM,0);

    bzero(&serveraddr,sizeof(serveraddr));
    serveraddr.sin_family =AF_INET;
    serveraddr.sin_addr.s_addr=htonl(INADDR_ANY);
    serveraddr.sin_port=htons(SERVER_PORT);
    //printf("%x\n",INADDR_ANY);
    bind(sockfd,(struct sockaddr*)&serveraddr,sizeof(serveraddr));
    while(1){    
        clientlen=sizeof(clientaddr);
        len=recvfrom(sockfd,buf,sizeof(buf),0,(struct sockaddr *)&clientaddr,&clientlen);

        printf("client IP %s\t PORT %d\n",
                inet_ntop(AF_INET,&clientaddr.sin_addr.s_addr,ipstr,sizeof(ipstr)),
                ntohs(clientaddr.sin_port));
        i=0;
        while(i<len){
            buf[i]=toupper(buf[i]);
            i++;
        }
        buf[i]=‘\0‘;
        sendto(sockfd,buf,len,0,(struct sockaddr*)&clientaddr,sizeof(clientaddr));
    }
    close(sockfd);
    return 0;
}

#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <ctype.h>
#define SERVER_PORT 5556 
#define MAXLINE 4096

int main(int argc,char *argv[])
{
    struct sockaddr_in serveraddr;
    int confd;
    ssize_t len;
    char ipstr[]="123.206.59.138";
    char buf[MAXLINE];
    if(argc <2){
        printf("./client str\n");
        exit(1);
    }
    //1.创建一个socket
    confd=socket(AF_INET,SOCK_DGRAM,0);
    //2.初始化服务器地址
    bzero(&serveraddr,sizeof(serveraddr));
    serveraddr.sin_family=AF_INET;
    //
    inet_pton(AF_INET,ipstr,&serveraddr.sin_addr.s_addr);
    serveraddr.sin_port =htons(SERVER_PORT);
    //3向务器发送数据
    sendto(confd,argv[1],strlen(argv[1]),0,(struct sockaddr *)&serveraddr,sizeof(serveraddr));

    len=recvfrom(confd,buf,sizeof(buf),0,NULL,0);
    write(STDIN_FILENO,buf,len);
    close(confd);
    return 0;
}