socket通信的简单实现

感觉socket的用法还是需要好好耐心的研究一下，先把理论的看懂，包括什么是socket，有哪些数据结构，哪些重要的函数和原理，再把人家的代码一句句看懂，最后最好自己写出来实践一下。不管的写的怎么样，总是自己的代码最好看懂。而且自己写的东西要负责，毕竟还是自己看的多。

下面是我参考人家的代码（其实都差不多），修修补补的写的一个实例，因为在Linux下的socket实现比较容易，更容易帮助理解socket的用法和原理。但是功能也比较简单，写的不清楚的请不吝赐教！

server.c

/* * Filename: server.c  * version 1.0 * Author :Halfish * Last edit time: March 2nd, 2014 */#include <netinet/in.h>   // for sockaddr_in#include <sys/types.h>    // for socket#include <sys/socket.h>   // for socket#include <stdio.h>        // for printf#include <errno.h>        // for errno#include <stdlib.h>       // for exit#include <string.h>       // for memset#define SERVER_PORT   6666 #define LENGTH_OF_LISTEN_QUEUE 20#define BUFFER_SIZE 1024int main(int argc, char const *argv[]){// 设置一个服务器端的socket地址结构server_addr,代表服务器internet地址, 端口struct sockaddr_in server_addr;int server_socket_fd; // 服务器端的文件描述符// define buffer to receive/send string from/to clientchar buffer_receive[BUFFER_SIZE];memset(buffer_receive, 0, BUFFER_SIZE);char buffer_send[BUFFER_SIZE];memset(buffer_send, 0, BUFFER_SIZE);   /** try to initialize to server address*/memset(&server_addr, 0, sizeof(server_addr)); //把一段内存区的内容全部设置为0    server_addr.sin_family = AF_INET;    server_addr.sin_addr.s_addr = htons(INADDR_ANY);    server_addr.sin_port = htons(SERVER_PORT);   /** try to creat a server socket*/server_socket_fd = socket(AF_INET, SOCK_STREAM, 0); if (server_socket_fd == -1){// only return -1 means fail and set errno simultaneouslyprintf("Failed to creat a socket for server...\n");printf("(errno: %d) %s\n", errno, strerror(errno) );return 1;}else{printf("Successfully creat a socket for server...\n");}   /** try to bind the server_socket_fd and server_addr*/if( bind(server_socket_fd,(struct sockaddr*)&server_addr, sizeof(server_addr) ) == -1)    {    // only return -1 means fail and set errno simultaneously        printf("Failed to bind this port: %d \n", SERVER_PORT);         printf("(errno: %d) %s\n", errno, strerror(errno) );        return 1;    }     else     {    // only bind returns 0 means bind successfully ?!        printf("Bind successfully\n");    }   /*    * the server begins to listen    */    if ( listen(server_socket_fd, LENGTH_OF_LISTEN_QUEUE) == -1)    {        printf("Failed to listen...");         printf("(errno: %d) %s \n", errno, strerror(errno));        return 1;    }    else     {        printf("Server is listening...\n");    }   /*    * begin connections to multiple clients    */    while(1)     {struct sockaddr_in client_address;        socklen_t length = sizeof(client_address);       /*        *        * 接受一个到server_socket代表的socket的一个连接        * 如果没有连接请求,就等待到有连接请求--这是accept函数的特性        * accept函数返回一个新的socket,这个socket(new_server_socket_fd)用于同连接到的客户的通信        * new_server_socket_fd代表了服务器和客户端之间的一个通信通道        * accept函数把连接到的客户端信息填写到客户端的socket地址结构client_address中        *        */        int new_server_socket_fd = accept(server_socket_fd, (struct sockaddr*)&client_address, &length);        if ( new_server_socket_fd < 0)        {            printf("Failed to accept a connection from to client!\n");            printf("(errno: %d) %s\n", errno, strerror(errno) );            break;        }         else        {            printf("Accepted a client successfully\n");        }// Thread added here        // accepted connection, begin a dead loop to receive information from one specific client        while(1)        {           /*        * recieve data from client        */        memset(buffer_receive, 0, BUFFER_SIZE);length = recv(new_server_socket_fd, buffer_receive, BUFFER_SIZE, 0);if (length < 0){printf("Failed to recieve data from client. \n" );printf("(errno: %d) %s\n", errno, strerror(errno) );continue;}else{printf("Client said:");printf("%s\n", buffer_receive);}           /*            * scanf from stdin continuously and send to client simutaneously        */        printf("Server(it's me) said:");        memset(buffer_send, 0, BUFFER_SIZE);        scanf("%s", buffer_send);               if (send(new_server_socket_fd, buffer_send, sizeof(buffer_send), 0) < 0)         {        printf("Failed to send data to client. \n" );printf("(errno: %d) %s\n", errno, strerror(errno) );continue;        }              } // end of while(1)   close(new_server_socket_fd);    }    close(server_socket_fd);return 0;}

client.c

/* * Filename: client.c  * version 1.0 * Author :Halfish * Last edit time: March 2nd, 2014 */#include <netinet/in.h>   // for sockaddr_in#include <sys/types.h>    // for socket#include <sys/socket.h>   // for socket#include <stdio.h>        // for printf#include <errno.h>        // for errno#include <stdlib.h>       // for exit#include <string.h>       // for memset#define SERVER_PORT  6666 #define BUFFER_SIZE  1024int main(int argc, char const *argv[]){    if (argc != 2)    {        printf("    You must tell me the address of server! \n");        return 0;    }   /*    * initilize client    */    int client_socket_fd = socket(AF_INET,SOCK_STREAM,0);    if (client_socket_fd == -1)    {        // only return -1 means fail and set errno simultaneously        printf("    Failed to creat a socket for client.\n");        printf("    (errno: %d) %s\n", errno, strerror(errno) );        return 1;    }    else     {        printf("    Successfully initilize the client !\n");    }   /*    * initilize server address    */    struct sockaddr_in server_address;    memset(&server_address, 0, sizeof(server_address));    server_address.sin_family = AF_INET;    if (inet_aton(argv[1],&server_address.sin_addr) == 0)  // inet_aton() = address to number    {        printf("    Server's IP address error!\n");        printf("    (errno: %d) %s\n", errno, strerror(errno) );        return 1;    }    server_address.sin_port = htons(SERVER_PORT);    socklen_t server_addr_length = sizeof(server_address);   /*    * begin to connect to server    */    if ( connect(client_socket_fd, (struct sockaddr*) &server_address, server_addr_length) == -1)    {        printf("    Can not connect to %s!\n", argv[1]);        printf("    (errno: %d) %s\n", errno, strerror(errno) );        return 1;    }    else    {        printf("    Successfully connect to server! \n");    }   /*    * define buffer to receive/send string from/to server    */    char buffer_receive[BUFFER_SIZE];     char buffer_send[BUFFER_SIZE];    memset(buffer_receive, 0, BUFFER_SIZE);    memset(buffer_send, 0, BUFFER_SIZE);    strcpy(buffer_send, "    I am the client, can you hear me ? ");    if (send(client_socket_fd, buffer_send, sizeof(buffer_send), 0) < 0)     {        printf("    Failed to send data to client. \n" );        printf("    (errno: %d) %s\n", errno, strerror(errno) );        return 0;    }         // accepted connection, begin a dead loop to receive information from one specific client    int i = 1;    while(i)    {        printf("%d\n", i);        ++ i;        /*        * recieve data from server        */        memset(buffer_receive, 0, BUFFER_SIZE);        socklen_t length = sizeof(server_address);        length = recv(client_socket_fd, buffer_receive, BUFFER_SIZE, 0);        if (length < 0)        {            printf("    Failed to recieve data from server. \n" );            printf("    (errno: %d) %s\n", errno, strerror(errno) );            continue;        }        else        {            printf("    Server said:");            printf("    %s\n", buffer_receive);        }       /*        * scanf from stdin continuously and send to server simutaneously        */        printf("    Client(it's me) said:   ");        memset(buffer_send, 0, BUFFER_SIZE);        scanf("%s", buffer_send);                   if (send(client_socket_fd, buffer_send, sizeof(buffer_send), 0) < 0)         {            printf("    Failed to send data to server. \n" );            printf("    (errno: %d) %s\n", errno, strerror(errno) );            continue;        }           } // end of while(1)          close(client_socket_fd);return 0;}