Simple Linux C Socket (01): Socket

概述

工作中用到了Linux C的网络编程，最近就又复习了相关的知识，留于此处。

原理

Linux C网络编程知识分为服务端和客户端编程：

• 服务端流程为：创建Socket-->绑定IP和端口-->启动监听-->等待客户端连接-->与客户端交互（读、写数据）-->关闭连接；
• 客户端流程为：创建Socket-->连接服务端-->与服务端交互（读、写数据）-->关闭连接；

代码

• 服务端代码(server.c)

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

int main(int argc, char *argv[])
{
  // check argv
  if (argc != 2)
  {
    printf("using: ./Server port\n");
    return -1;
  }

  // create socket server
  int listenFd;
  if ((listenFd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
  {
    perror("socket");
    return -1;
  }

  // bind
  struct sockaddr_in serverAddr;
  memset(&serverAddr, 0, sizeof(serverAddr));
  serverAddr.sin_family = AF_INET;
  serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
  serverAddr.sin_port = htons(atoi(argv[1]));
  if (bind(listenFd, (struct sockaddr *)&serverAddr, sizeof(serverAddr)) != 0)
  {
    perror("bind");
    return -1;
  }

  // listen
  if (listen(listenFd, 5) != 0)
  {
    perror("listen");
    close(listenFd);
    return -1;
  }

  // accept
  int clientFd;
  int socklen = sizeof(struct sockaddr_in);
  struct sockaddr_in clientAddr;
  clientFd = accept(listenFd, (struct sockaddr_in *)&clientAddr, (socklen_t *)&socklen);
  printf("客户端已连接...\n");

  // send recv
  char buffer[1024];
  while (1)
  {
    int nRet;
    memset(buffer, 0, sizeof(buffer));
    if ((nRet = recv(clientFd, buffer, sizeof(buffer), 0)) <= 0)
    {
      printf("recv ret=%d\n", nRet);
      break;
    }
    printf("接收: %s\n", buffer);

    strcpy(buffer, "Ok");
    if ((nRet = send(clientFd, buffer, strlen(buffer), 0)) <= 0)
    {
      perror("send");
      break;
    }
    printf("发送: %s\n", buffer);
  }

  close(listenFd);
  close(clientFd);
}

• 客户端代码(client.c)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

int main( int argc, char* argv[] )
{
    //check
    if( argc != 3 )
    {
        printf( "Using: ./client ip port\n" );
        return -1;
    }

    //create socket
    int sockFd;
    if( ( sockFd = socket( AF_INET,SOCK_STREAM, 0 ) ) == -1 )
    {
        perror( "socket" );
        return -1;
    }
    printf( "create socket finished\n" );

    //connect
    struct hostent* pHost;
    if( ( pHost = gethostbyname( argv[1] ) ) == 0 )
    {
        printf( "gethostbyname failed! \n" );
        close( sockFd );
        return -1;
    }
    printf( "gethostbyname finished\n" );

    struct sockaddr_in serverAddr;
    memset( &serverAddr, 0, sizeof( serverAddr ) );
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons( atoi( argv[2] ) );
    printf( "sin_port finished\n" );
    memcpy( &serverAddr.sin_addr, pHost->h_addr, pHost->h_length );
    memcpy( &serverAddr.sin_addr, pHost->h_addr, pHost->h_length );
    printf( "sin_addr finished\n" );
    if( connect( sockFd, ( struct sockaddr* )&serverAddr, sizeof( serverAddr ) ) != 0 )
    {
        perror( "connect" );
        close( sockFd );
        return -1;
    }
    printf( "connect finished\n" );

    //send recv
    char buffer[ 1024 ];
    for( int n = 0; n < 3; n++ )
    {
        int nRet;
        memset( buffer, 0, sizeof( buffer ) );
        sprintf( buffer, "%d--啊哈哈哈哈", n+1 );
        if( ( nRet = send( sockFd, buffer, strlen( buffer ), 0 ) ) <= 0 )
        {
            perror( "send" );
            close( sockFd );
            return -1;
        }
        printf( "发送：%s\n", buffer );

        memset( buffer, 0, sizeof( buffer ) );
        if( ( nRet = recv( sockFd, buffer, sizeof( buffer ), 0 ) ) <= 0 )
        {
            printf( "recv ret=%d\n", nRet );
            break;
        }
        printf( "接收：%s\n", buffer );
    }

    //close
    close( sockFd );
}

编译代码

gcc -o server server.c
gcc -o client client.c