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  • 网络编程学习,给程序做注释

    从github上找了3段程序,借此来学习socket编程,从一开始看不懂,到现在能看出来个轮廓,还是有进步的。

    #注意,本文所示程序除注释外均非本人所写。

     1 #ifndef SERVER_H
     2 #define SERVER_H            // line 3 to 11 : include lib
     3 #include <unistd.h>
     4 #include <stdio.h>
     5 #include <stdlib.h>
     6 #include <unistd.h>
     7 #include <string.h>
     8 #include <sys/types.h>
     9 #include <sys/socket.h>
    10 #include <netinet/in.h>
    11 #include <netdb.h>
    12 
    13 struct Server;                //声明结构体
    14 
    15 struct Server * new_server(char *host, char *port); //声明函数
    16 
    17 //主机连接函数
    18 int host_connect(struct Server *this);
    19 //信息接收
    20 char *get_message(struct Server *this);
    21 //信息发送函数
    22 void send_message(struct Server *this, const char *msg);
    23 // 错误处理函数
    24 void error(struct Server *this, const char *msg);
    25 
    26 struct Server {
    27   int port;                        //端口
    28   char *host;                    //主机地址
    29 
    30   int sockfd;                    //描述符
    31   char buffer[256];                //应该是传送的信息
    32 
    33   int (*host_connect)(struct Server *this);//函数指针
    34   char *(*get_message)(struct Server *this);
    35   void (*send_message)(struct Server *this, const char *msg);
    36   void (*error)(struct Server *this, const char *msg);
    37 
    38   struct sockaddr_in server_address;;
    39   struct hostent *server;
    40 };
    41 
    42 #endif
     1 #include "server.h"
     2 
     3 //函数名字为new_server的返回值是指向结构体Server的指针
     4 struct Server * new_server(char *host, char *port) {
     5   struct Server *server = malloc(sizeof(struct Server));
     6 
     7   // line 8~13 赋值
     8   server->host_connect = &host_connect;
     9   server->get_message = &get_message;
    10   server->send_message = &send_message;
    11   server->error = &error;
    12   server->host = host;
    13   server->port = atoi(port);
    14   
    15   return server;
    16 }
    17 
    18 int host_connect(struct Server *this) {
    19   // int socket(int domain,int type,int protocol);
    20   //                域            类型      协议
    21   //创建套接字
    22   // AF_INET  IPv4因特网域
    23   // SOCK_STREAM  有序,可靠,双向到面向连接字节流
    24   // AF_INET + SOCK_STREAM ----->  tcp协议
    25   this->sockfd = socket(AF_INET, SOCK_STREAM, 0);
    26   if (this->sockfd < 0) {
    27     return 0;
    28   }
    29 
    30   this->server = gethostbyname(this->host);
    31   if (this->server == NULL) {
    32     return 0;
    33   }
    34 
    35   //bzero函数功能,置字节字符串s到前n个字节为零且包括''
    36   bzero((char *) &this->server_address, sizeof(this->server_address));
    37   this->server_address.sin_family = AF_INET;
    38 
    39   //bcopy函数功能应该和bzero差不多
    40   //extern void bcopy(const void *src,void *dest,int n);
    41   //将字符串src到前n个字节复制到dest中
    42   bcopy((char *)this->server->h_addr,
    43         (char *)&this->server_address.sin_addr.s_addr,
    44         this->server->h_length);
    45 
    46   this->server_address.sin_port = htons(this->port);
    47 
    48   if (connect(this->sockfd,
    49       (struct sockaddr *) &this->server_address,
    50       sizeof(this->server_address)) < 0) {
    51     this->error(this, "Could not connect to host!");
    52   }
    53 
    54   return 1;
    55 }
    56 
    57 char * get_message(struct Server *this) {
    58   bzero(this->buffer, 256);
    59 
    60   if(read(this->sockfd, this->buffer, 255) < 0) {
    61     this->error(this, "Error reading from socket");
    62   }
    63 
    64   return this->buffer;
    65 }
    66 
    67 void send_message(struct Server *this, const char *msg) {
    68   bzero(this->buffer, 256);
    69 
    70   if(write(this->sockfd, msg, strlen(msg)) < 0) {
    71     this->error(this, "Error writing to socket");
    72   }
    73 }
    74 
    75 void error(struct Server *this, const char *msg) {
    76   perror(msg);
    77   close(this->sockfd);
    78   exit(-1);
    79 }
     1 #include "server.h"
     2 
     3 int main(int argc, char *argv[]) {
     4   if (argc < 2) {
     5     puts("Usage: ./chat [ip address] [port]");
     6     return -1;
     7   }
     8 
     9   char *line;
    10   size_t length = 80;
    11 
    12   struct Server *server = new_server(argv[1], argv[2]);
    13   server->host_connect(server);
    14 
    15   printf("## %s
    ", server->get_message(server));
    16 
    17   while (1) {
    18     printf("> ");
    19     fflush(stdout);
    20 
    21     if (getline(&line, &length, stdin) < 0) {
    22       server->error(server, "Error while getting input!");
    23     }
    24 
    25     if (strcmp(line, "/quit
    ") == 0) {
    26       puts("Goodbye!");
    27       break;
    28     }
    29 
    30     server->send_message(server, line);
    31     printf("## %s
    ", server->get_message(server));
    32   }
    33 
    34   close(server->sockfd);
    35   return 0;
    36 }
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  • 原文地址:https://www.cnblogs.com/symons1992/p/3541394.html
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