今天在linux系統上寫了一個簡單的socket檔案傳輸的例子，共享出來僅供參考。例子很簡單，只要初學者瞭解簡單的幾個socket相關函式和檔案函式就能寫的出來。

伺服器端程式：

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/shm.h>

#define BUF_SIZE      1024
#define SERVER_PORT   1234

int main()
{
char *filename = "sendfile.txt";
FILE *fp = fopen(filename,"rb" );
if(fp == NULL )
{
printf("open file error!!\r\n");
exit(1);
}
else
{
printf("open file succeed\r\n");
}

int server_sockfd = socket(AF_INET,SOCK_STREAM,0);
///bind listen
struct sockaddr_in server_sockAddr;
memset(&server_sockAddr,0 , sizeof(server_sockAddr));
server_sockAddr.sin_family = PF_INET;
server_sockAddr.sin_addr.s_addr = htonl(INADDR_ANY);
server_sockAddr.sin_port = htons(SERVER_PORT);

if(bind(server_sockfd,(struct sockaddr *)&server_sockAddr,\
sizeof(server_sockAddr) ) == -1)
{
perror("bind error\r\n");
exit(1);
}

if(listen(server_sockfd,20) == -1)
{
perror("listen error\r\n");
exit(1);
}

///accept
struct sockaddr_in client_addr;
int clnSize = sizeof(client_addr);
int conn = accept(server_sockfd,(struct sockaddr*)&client_addr,&clnSize);
if(conn <0)
{
perror("accept error!\r\n");
exit(1);
}

/// 迴圈傳送檔案直到末尾；
char buffer[BUF_SIZE]={0};
int send_len = 0;
while((send_len = fread(buffer,1, BUF_SIZE,fp)) >0)
{
    send(conn, buffer, send_len, 0);
}
shutdown( conn, SHUT_WR);
recv(conn,buffer,BUF_SIZE, 0);

fclose(fp);
close(conn);
close(server_sockfd);

return 0;
}
 

客戶端程式：

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/shm.h>


int main()
{
///手動輸入建立你檔案
char filename[100]; //儲存檔名
printf("input the file name: ");
gets(filename);
//scanf("Input file name to save:%s ", filename);
FILE *fp = fopen(filename, "wb");
if(fp == NULL){
printf("open file failed!!\r\n");
exit(1);
}

//定義客戶端socketfd
int sock_cli = socket(PF_INET,SOCK_STREAM, IPPROTO_TCP);

//connect
struct sockaddr_in serveraddr;
serveraddr.sin_family = PF_INET;
serveraddr.sin_port = htons(1234);
serveraddr.sin_addr.s_addr =inet_addr("127.0.0.1");

if (connect(sock_cli,(struct sockaddr *)&serveraddr,sizeof(serveraddr)) <0)
{
	perror("connect failed!\r\n");
	exit(1);
}
int ncount = 0;
char recvbuf[1024] = {0};
while( (ncount = recv(sock_cli, recvbuf, 1024, 0)) >0) {
    
fwrite(recvbuf, 1, ncount, fp);
}

puts("file transfer succeed!!\r\n");
memset(recvbuf, 0, 1024);
fclose(fp);
close(sock_cli);
return 0;
}
 

先執行伺服器端的程式

再執行客戶端的程式：

完了後你會發現當前目錄下多了一個你在客戶端手動建立的檔案，檔案內容與伺服器端傳送過來的檔案內容一致!

總結下：其實呢，socket的檔案傳輸和socket一般的字串通訊差不多的，將檔案的內容讀出來傳送到對端而已。