實例來自互聯網，這段測試代碼實現了基本的文件傳輸原理，沒有實現錯誤處理。
//////////////////////////////////////////////////////////////////////////////////////
// file_server.c? 文件傳輸順序服務器示例
//////////////////////////////////////////////////////////////////////////////////////
//本文件是服務器的代碼
#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 <stdlib.h>??? ??? // for exit
#include <string.h>??? ??? // for bzero
/*
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
*/
#define HELLO_WORLD_SERVER_PORT??? 6666
#define LENGTH_OF_LISTEN_QUEUE? 20
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512
int main(int argc, char **argv)
{
??? //設置一個socket地址結構server_addr,代表服務器internet地址, 端口
??? struct sockaddr_in server_addr;
??? bzero(&server_addr,sizeof(server_addr)); //把一段內存區的內容全部設置為0
??? server_addr.sin_family = AF_INET;
??? server_addr.sin_addr.s_addr = htons(INADDR_ANY);
??? server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);
??? //創建用于internet的流協議(TCP)socket,用server_socket代表服務器socket
??? int server_socket = socket(PF_INET,SOCK_STREAM,0);
??? if( server_socket < 0)
??? {
??? ??? printf("Create Socket Failed!");
??? ??? exit(1);
??? }
???
??? //把socket和socket地址結構聯系起來
??? if( bind(server_socket,(struct sockaddr*)&server_addr,sizeof(server_addr)))
??? {
??? ??? printf("Server Bind Port : %d Failed!", HELLO_WORLD_SERVER_PORT);
??? ??? exit(1);
??? }
???
??? //server_socket用于監聽
??? if ( listen(server_socket, LENGTH_OF_LISTEN_QUEUE) )
??? {
??? ??? printf("Server Listen Failed!");
??? ??? exit(1);
??? }
??? while (1) //服務器端要一直運行
??? {
??? ??? //定義客戶端的socket地址結構client_addr
??? ??? struct sockaddr_in client_addr;
??? ??? socklen_t length = sizeof(client_addr);
??? ??? //接受一個到server_socket代表的socket的一個連接
??? ??? //如果沒有連接請求,就等待到有連接請求--這是accept函數的特性
??? ??? //accept函數返回一個新的socket,這個socket(new_server_socket)用于同連接到的客戶的通信
??? ??? //new_server_socket代表了服務器和客戶端之間的一個通信通道
??? ??? //accept函數把連接到的客戶端信息填寫到客戶端的socket地址結構client_addr中
??? ??? int new_server_socket = accept(server_socket,(struct sockaddr*)&client_addr,&length);
??? ??? if ( new_server_socket < 0)
??? ??? {
??? ??? ??? printf("Server Accept Failed!\n");
??? ??? ??? break;
??? ??? }
??? ???
??? ??? char buffer[BUFFER_SIZE];
??? ??? bzero(buffer, BUFFER_SIZE);
??? ??? length = recv(new_server_socket,buffer,BUFFER_SIZE,0);//這里先接收客戶端發來的要獲取的文件名
??????? if (length < 0)
??? ??? {
??? ??? ??? printf("Server Recieve Data Failed!\n");
??? ??? ??? break;
??? ??? }
??? ??? 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));
//??? ??? int fp = open(file_name, O_RDONLY);
//??? ??? if( fp < 0 )
??? ??? FILE * fp = fopen(file_name,"r");
??? ??? if(NULL == fp )
??? ??? {
??? ??? ??? printf("File:\t%s Not Found\n", file_name);
??? ??? }
??? ??? else
??? ??? {
??? ??? ??? bzero(buffer, BUFFER_SIZE);
??? ??? ??? int file_block_length = 0;
//??? ??? ??? while( (file_block_length = read(fp,buffer,BUFFER_SIZE))>0)
??? ??? ??? while( (file_block_length = fread(buffer,sizeof(char),BUFFER_SIZE,fp))>0)
??? ??? ??? {
??? ??? ??? ??? printf("file_block_length = %d\n",file_block_length);
??? ??? ??? ??? //發送buffer中的字符串到new_server_socket,實際是給客戶端
??? ??? ??? ??? if(send(new_server_socket,buffer,file_block_length,0)<0)
??? ??? ??? ??? {
??? ??? ??? ??? ??? printf("Send File:\t%s Failed\n", file_name);
??? ??? ??? ??? ??? break;
??? ??? ??? ??? }
??? ??? ??? ??? bzero(buffer, BUFFER_SIZE);
??? ??? ??? }???????????????????????????????????????????????????????????????? //這段代碼是循環讀取文件的一段數據，在循環調用send，發送到客戶端，這里強調一點的TCP每次接受最多是1024字節，多了就會分片，因此每次發送時盡量不要超過1024字節。
//??? ??? ??? close(fp);
??? ??? ??? fclose(fp);
??? ??? ??? printf("File:\t%s Transfer Finished\n",file_name);
??? ??? }
??? ??? //關閉與客戶端的連接
??? ??? close(new_server_socket);
??? }
??? //關閉監聽用的socket
??? close(server_socket);
??? return 0;
}
//////////////////////////////////////////////////////////////////////////////////////
// file_client.c? 文件傳輸客戶端程序示例
//////////////////////////////////////////////////////////////////////////////////////
//本文件是客戶機的代碼
#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 <stdlib.h>??? ??? // for exit
#include <string.h>??? ??? // for bzero
/*
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
*/
#define HELLO_WORLD_SERVER_PORT??? 6666
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512
int main(int argc, char **argv)
{
??? if (argc != 2)
??? {
??? ??? printf("Usage: ./%s ServerIPAddress\n",argv[0]);
??? ??? exit(1);
??? }
??? //設置一個socket地址結構client_addr,代表客戶機internet地址, 端口
??? struct sockaddr_in client_addr;
??? bzero(&client_addr,sizeof(client_addr)); //把一段內存區的內容全部設置為0
??? client_addr.sin_family = AF_INET;??? //internet協議族
??? client_addr.sin_addr.s_addr = htons(INADDR_ANY);//INADDR_ANY表示自動獲取本機地址
??? client_addr.sin_port = htons(0);??? //0表示讓系統自動分配一個空閑端口
??? //創建用于internet的流協議(TCP)socket,用client_socket代表客戶機socket
??? int client_socket = socket(AF_INET,SOCK_STREAM,0);
??? if( client_socket < 0)
??? {
??? ??? printf("Create Socket Failed!\n");
??? ??? exit(1);
??? }
??? //把客戶機的socket和客戶機的socket地址結構聯系起來
??? if( bind(client_socket,(struct sockaddr*)&client_addr,sizeof(client_addr)))
??? {
??? ??? printf("Client Bind Port Failed!\n");
??? ??? exit(1);
??? }
??? //設置一個socket地址結構server_addr,代表服務器的internet地址, 端口
??? struct sockaddr_in server_addr;
??? bzero(&server_addr,sizeof(server_addr));
??? server_addr.sin_family = AF_INET;
??? if(inet_aton(argv[1],&server_addr.sin_addr) == 0) //服務器的IP地址來自程序的參數
??? {
??? ??? printf("Server IP Address Error!\n");
??? ??? exit(1);
??? }
??? server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);
??? socklen_t server_addr_length = sizeof(server_addr);
??? //向服務器發起連接,連接成功后client_socket代表了客戶機和服務器的一個socket連接
??? if(connect(client_socket,(struct sockaddr*)&server_addr, server_addr_length) < 0)
??? {
??? ??? printf("Can Not Connect To %s!\n",argv[1]);
??? ??? exit(1);
??? }
??? 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));
??? //向服務器發送buffer中的數據
??? send(client_socket,buffer,BUFFER_SIZE,0);
//??? int fp = open(file_name, O_WRONLY|O_CREAT);
//??? if( fp < 0 )
??? FILE * fp = fopen(file_name,"w");
??? if(NULL == fp )
??? {
??? ??? printf("File:\t%s Can Not Open To Write\n", file_name);
??? ??? exit(1);
??? }
???
??? //從服務器接收數據到buffer中
??? bzero(buffer,BUFFER_SIZE);
??? int length = 0;
??? while( length = recv(client_socket,buffer,BUFFER_SIZE,0))???????//循環接收，再寫到文件
??? {
??? ??? if(length < 0)
??? ??? {
??? ??? ??? printf("Recieve Data From Server %s Failed!\n", argv[1]);
??? ??? ??? break;
??? ??? }
//??? ??? int write_length = write(fp, buffer,length);
??? ??? int write_length = fwrite(buffer,sizeof(char),length,fp);
??? ??? if (write_length<length)
??? ??? {
??? ??? ??? printf("File:\t%s Write Failed\n", file_name);
??? ??? ??? break;
??? ??? }
??? ??? bzero(buffer,BUFFER_SIZE);???
??? }
??? printf("Recieve File:\t %s From Server[%s] Finished\n",file_name, argv[1]);
???
??? close(fp);
??? //關閉socket
??? close(client_socket);
??? return 0;
}