Linux C语言socket编程详解
避免大家浪费时间找教材以及万恶的积分下载，分享这本书，仅供学习参考：计算机网络第七版谢希仁pdf下载
编者是在linux系统rk3308和android系统aml905上验证的，例子不难，但跨平台验证时，需要注意如何编译等一些基础知识，比如Android系统源码external添加新模块。
接口简介
socket()：创建socket
bind()：绑定socket到本地地址和端口，通常由服务端调用
listen()：TCP专用，开启监听模式
accept()：TCP专用，服务器等待客户端连接，一般是阻塞态
connect()：TCP专用，客户端主动连接服务器
send()：TCP专用，发送数据
recv()：TCP专用，接收数据
sendto()：UDP专用，发送数据到指定的IP地址和端口
recvfrom()：UDP专用，接收数据，返回数据远端的IP地址和端口
closesocket()：关闭socket
流程
1. 编写server
/*************************************************************************
> File Name: Server.c
> Author : Rick
> Date : 2020/05/07
************************************************************************/
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#define SERVER_PORT 8000
#define LENGTH_OF_LISTEN_QUEUE 20
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512
int main(void)
{
// 声明并初始化一个服务器端的socket地址结构
struct sockaddr_in server_addr;
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htons(INADDR_ANY);
server_addr.sin_port = htons(SERVER_PORT);
// 创建socket，若成功，返回socket描述符
int server_socket_fd = socket(PF_INET, SOCK_STREAM, 0);
if(server_socket_fd < 0)
{
perror("Create Socket Failed:");
exit(1);
}
int opt = 1;
setsockopt(server_socket_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
// 绑定socket和socket地址结构
if(-1 == (bind(server_socket_fd, (struct sockaddr*)&server_addr, sizeof(server_addr))))
{
perror("Server Bind Failed:");
exit(1);
}
// socket监听
if(-1 == (listen(server_socket_fd, LENGTH_OF_LISTEN_QUEUE)))
{
perror("Server Listen Failed:");
exit(1);
}
printf("Prepared... \n");
while(1)
{
// 定义客户端的socket地址结构
struct sockaddr_in client_addr;
socklen_t client_addr_length = sizeof(client_addr);
// 接受连接请求，返回一个新的socket(描述符)，这个新socket用于同连接的客户端通信
// accept函数会把连接到的客户端信息写到client_addr中
int new_server_socket_fd = accept(server_socket_fd, (struct sockaddr*)&client_addr, &client_addr_length);
if(new_server_socket_fd < 0)
{
perror("Server Accept Failed:");
break;
}
// recv函数接收数据到缓冲区buffer中
char buffer[BUFFER_SIZE];
bzero(buffer, BUFFER_SIZE);
if(recv(new_server_socket_fd, buffer, BUFFER_SIZE, 0) < 0)
{
perror("Server Recieve Data Failed:");
break;
}
// 然后从buffer(缓冲区)拷贝到file_name中
char file_name[FILE_NAME_MAX_SIZE+1];
bzero(file_name, FILE_NAME_MAX_SIZE+1);
strncpy(file_name, buffer, strlen(buffer)>FILE_NAME_MAX_SIZE?FILE_NAME_MAX_SIZE:strlen(buffer));
printf("%s\n", file_name);
// 打开文件并读取文件数据
FILE *fp = fopen(file_name, "r");
if(NULL == fp)
{
printf("File:%s Not Found\n", file_name);
}
else
{
bzero(buffer, BUFFER_SIZE);
int length = 0;
// 每读取一段数据，便将其发送给客户端，循环直到文件读完为止
while((length = fread(buffer, sizeof(char), BUFFER_SIZE, fp)) > 0)
{
if(send(new_server_socket_fd, buffer, length, 0) < 0)
{
printf("Send File:%s Failed./n", file_name);
break;
}
bzero(buffer, BUFFER_SIZE);
}
// 关闭文件
fclose(fp);
printf("File:%s Transfer Successful!\n", file_name);
}
// 关闭与客户端的连接
close(new_server_socket_fd);
}
// 关闭监听用的socket
close(server_socket_fd);
return 0;
}
2.编写client
/*************************************************************************
> File Name: Client.c
> Author : Rick
> Date : 2020/05/07
************************************************************************/
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<arpa/inet.h>
#define SERVER_PORT 8000
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512
int main()
{
// 声明并初始化一个客户端的socket地址结构
struct sockaddr_in client_addr;
bzero(&client_addr, sizeof(client_addr));
client_addr.sin_family = AF_INET;
client_addr.sin_addr.s_addr = htons(INADDR_ANY);
client_addr.sin_port = htons(0);
// 创建socket，若成功，返回socket描述符
int client_socket_fd = socket(AF_INET, SOCK_STREAM, 0);
if(client_socket_fd < 0)
{
perror("Create Socket Failed:");
exit(1);
}
// 绑定客户端的socket和客户端的socket地址结构 非必需
if(-1 == (bind(client_socket_fd, (struct sockaddr*)&client_addr, sizeof(client_addr))))
{
perror("Client Bind Failed:");
exit(1);
}
// 声明一个服务器端的socket地址结构，并用服务器那边的IP地址及端口对其进行初始化，用于后面的连接
struct sockaddr_in server_addr;
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
if(inet_pton(AF_INET, "127.0.0.1", &server_addr.sin_addr) == 0)
{
perror("Server IP Address Error:");
exit(1);
}
server_addr.sin_port = htons(SERVER_PORT);
socklen_t server_addr_length = sizeof(server_addr);
// 向服务器发起连接，连接成功后client_socket_fd代表了客户端和服务器的一个socket连接
if(connect(client_socket_fd, (struct sockaddr*)&server_addr, server_addr_length) < 0)
{
perror("Can Not Connect To Server IP:");
exit(0);
}
// 输入文件名 并放到缓冲区buffer中等待发送
char file_name[FILE_NAME_MAX_SIZE+1];
bzero(file_name, FILE_NAME_MAX_SIZE+1);
printf("Please Input File Name On Server:\t");
scanf("%s", file_name);
char buffer[BUFFER_SIZE];
bzero(buffer, BUFFER_SIZE);
strncpy(buffer, file_name, strlen(file_name)>BUFFER_SIZE?BUFFER_SIZE:strlen(file_name));
// 向服务器发送buffer中的数据
if(send(client_socket_fd, buffer, BUFFER_SIZE, 0) < 0)
{
perror("Send File Name Failed:");
exit(1);
}
// 打开文件，准备写入
FILE *fp = fopen(file_name, "w");
if(NULL == fp)
{
printf("File:\t%s Can Not Open To Write\n", file_name);
exit(1);
}
printf("Prepared... \n");
// 从服务器接收数据到buffer中
// 每接收一段数据，便将其写入文件中，循环直到文件接收完并写完为止
bzero(buffer, BUFFER_SIZE);
int length = 0;
while((length = recv(client_socket_fd, buffer, BUFFER_SIZE, 0)) > 0)
{
printf("receiving... \n");
if(fwrite(buffer, sizeof(char), length, fp) < length)
{
printf("File:\t%s Write Failed\n", file_name);
break;
}
bzero(buffer, BUFFER_SIZE);
}
// 接收成功后，关闭文件，关闭socket
printf("Receive File:\t%s From Server IP Successful!\n", file_name);
fclose(fp);
close(client_socket_fd);
return 0;
}
3.编译
略，根据实际执行硬件平台，配置相关编译交叉工具等。
4.验证
/oem # ./server_3308
./server_3308
Prepared...
server_3308
File:server_3308 Transfer Successful!
参考链接：