diff --git a/src/include/gpxe/tcp.h b/src/include/gpxe/tcp.h
new file mode 100644
index 00000000..c6611144
--- /dev/null
+++ b/src/include/gpxe/tcp.h
@@ -0,0 +1,102 @@
+#ifndef _TCP_H
+#define _TCP_H
+
+/** @file
+ *
+ * TCP protocol
+ *
+ * This file defines the gPXE TCP API.
+ *
+ */
+
+#include <stddef.h>
+#include <gpxe/in.h>
+
+struct tcp_connection;
+
+/**
+ * TCP operations
+ *
+ */
+struct tcp_operations {
+	/**
+	 * Connection aborted (RST received)
+	 *
+	 * @v conn	TCP connection
+	 */
+	void ( * aborted ) ( struct tcp_connection *conn );
+	/**
+	 * Connection timed out
+	 *
+	 * @v conn	TCP connection
+	 */
+	void ( * timedout ) ( struct tcp_connection *conn );
+	/**
+	 * Connection aborted (FIN received)
+	 *
+	 * @v conn	TCP connection
+	 *
+	 * Note that acked() and newdata() may be called after
+	 * closed(), if the packet containing the FIN also
+	 * acknowledged data or contained new data.
+	 */
+	void ( * closed ) ( struct tcp_connection *conn );
+	/**
+	 * Connection established (SYNACK received)
+	 *
+	 * @v conn	TCP connection
+	 */
+	void ( * connected ) ( struct tcp_connection *conn );
+	/**
+	 * Data acknowledged
+	 *
+	 * @v conn	TCP connection
+	 * @v len	Length of acknowledged data
+	 *
+	 * @c len is guaranteed to not exceed the outstanding amount
+	 * of unacknowledged data.
+	 */
+	void ( * acked ) ( struct tcp_connection *conn, size_t len );
+	/**
+	 * New data received
+	 *
+	 * @v conn	TCP connection
+	 * @v data	Data
+	 * @v len	Length of data
+	 */
+	void ( * newdata ) ( struct tcp_connection *conn,
+			     void *data, size_t len );
+	/**
+	 * Transmit data
+	 *
+	 * @v conn	TCP connection
+	 *
+	 * The application should transmit whatever it currently wants
+	 * to send using tcp_send().  If retransmissions are required,
+	 * senddata() will be called again and the application must
+	 * regenerate the data.  The easiest way to implement this is
+	 * to ensure that senddata() never changes the application's
+	 * state.
+	 */
+	void ( * senddata ) ( struct tcp_connection *conn );
+};
+
+/**
+ * A TCP connection
+ *
+ */
+struct tcp_connection {
+	/** Address of the remote end of the connection */
+	struct sockaddr_in sin;
+	/** Operations table for this connection */
+	struct tcp_operations *tcp_op;
+};
+
+extern int tcp_connect ( struct tcp_connection *conn );
+extern void tcp_send ( struct tcp_connection *conn, const void *data,
+		       size_t len );
+extern void tcp_close ( struct tcp_connection *conn );
+extern void init_tcpip ( void );
+extern void run_tcpip ( void );
+
+#endif /* _TCP_H */
diff --git a/src/proto/tcp.c b/src/proto/tcp.c
new file mode 100644
index 00000000..8c732015
--- /dev/null
+++ b/src/proto/tcp.c
@@ -0,0 +1,206 @@
+#include <string.h>
+#include <assert.h>
+#include <byteswap.h>
+#include <gpxe/tcp.h>
+#include "uip/uip.h"
+#include "uip/uip_arp.h"
+
+/** @file
+ *
+ * TCP protocol
+ *
+ * The gPXE TCP stack is currently implemented on top of the uIP
+ * protocol stack.  This file provides wrappers around uIP so that
+ * higher-level protocol implementations do not need to talk directly
+ * to uIP (which has a somewhat baroque API).
+ *
+ * Basic operation is to create a #tcp_connection structure, call
+ * tcp_connect() and then call run_tcpip() in a loop until the
+ * operation has completed.  The TCP stack will call the various
+ * methods defined in the #tcp_operations structure in order to send
+ * and receive data.
+ *
+ * See hello.c for a trivial example of a TCP protocol using this
+ * API.
+ *
+ */
+
+/**
+ * Initialise TCP/IP stack
+ *
+ */
+void init_tcpip ( void ) {
+	uip_init();
+	uip_arp_init();
+}
+
+#define UIP_HLEN ( 40 + UIP_LLH_LEN )
+
+/**
+ * Transmit TCP data
+ *
+ * This is a wrapper around netdev_transmit().  It gathers up the
+ * packet produced by uIP, and then passes it to netdev_transmit() as
+ * a single buffer.
+ */
+static void uip_transmit ( void ) {
+	uip_arp_out();
+	if ( uip_len > UIP_HLEN ) {
+		memcpy ( uip_buf + UIP_HLEN, ( void * ) uip_appdata,
+			 uip_len - UIP_HLEN );
+	}
+	netdev_transmit ( uip_buf, uip_len );
+	uip_len = 0;
+}
+
+/**
+ * Run the TCP/IP stack
+ *
+ * Call this function in a loop in order to allow TCP/IP processing to
+ * take place.  This call takes the stack through a single iteration;
+ * it will typically be used in a loop such as
+ *
+ * @code
+ *
+ * struct tcp_connection *my_connection;
+ * ...
+ * tcp_connect ( my_connection );
+ * while ( ! my_connection->finished ) {
+ *   run_tcpip();
+ * }
+ *
+ * @endcode
+ *
+ * where @c my_connection->finished is set by one of the connection's
+ * #tcp_operations methods to indicate completion.
+ */
+void run_tcpip ( void ) {
+	void *data;
+	size_t len;
+	uint16_t type;
+	int i;
+	
+	if ( netdev_poll ( 1, &data, &len ) ) {
+		/* We have data */
+		memcpy ( uip_buf, data, len );
+		uip_len = len;
+		type = ntohs ( *( ( uint16_t * ) ( uip_buf + 12 ) ) );
+		if ( type == UIP_ETHTYPE_ARP ) {
+			uip_arp_arpin();
+		} else {
+			uip_arp_ipin();
+			uip_input();
+		}
+		if ( uip_len > 0 )
+			uip_transmit();
+	} else {
+		for ( i = 0 ; i < UIP_CONNS ; i++ ) {
+			uip_periodic ( i );
+			if ( uip_len > 0 )
+				uip_transmit();
+		}
+	}
+}
+
+/**
+ * Open a TCP connection
+ *
+ * @v conn	TCP connection
+ * @ret 0	Success
+ * @ret <0	Failure
+ * 
+ * This sets up a new TCP connection to the remote host specified in
+ * tcp_connection::sin.  The actual SYN packet will not be sent out
+ * until run_tcpip() is called for the first time.
+ *
+ * @todo Use linked lists instead of a static buffer, and thereby
+ *       remove the only potential failure case, giving this function
+ *       a void return type.
+ */
+int tcp_connect ( struct tcp_connection *conn ) {
+	struct uip_conn *uip_conn;
+	u16_t ipaddr[2];
+
+	assert ( conn->sin.sin_addr.s_addr != 0 );
+	assert ( conn->sin.sin_port != 0 );
+	assert ( conn->tcp_op != NULL );
+	assert ( sizeof ( uip_conn->appstate ) == sizeof ( conn ) );
+
+	* ( ( uint32_t * ) ipaddr ) = conn->sin.sin_addr.s_addr;
+	uip_conn = uip_connect ( ipaddr, conn->sin.sin_port );
+	if ( ! uip_conn )
+		return -1;
+
+	*( ( void ** ) uip_conn->appstate ) = conn;
+	return 0;
+}
+
+/**
+ * Send data via a TCP connection
+ *
+ * @v conn	TCP connection
+ * @v data	Data to send
+ * @v len	Length of data
+ *
+ * Data will be automatically limited to the current TCP window size.
+ *
+ * If retransmission is required, the connection's
+ * tcp_operations::newdata() method will be called again in order to
+ * regenerate the data.
+ */
+void tcp_send ( struct tcp_connection *conn __unused,
+		const void *data, size_t len ) {
+	assert ( conn = *( ( void ** ) uip_conn->appstate ) );
+	uip_send ( ( void * ) data, len );
+}
+
+/**
+ * Close a TCP connection
+ *
+ * @v conn	TCP connection
+ */
+void tcp_close ( struct tcp_connection *conn __unused ) {
+	assert ( conn = *( ( void ** ) uip_conn->appstate ) );
+	uip_close();
+}
+
+/**
+ * uIP TCP application call interface
+ *
+ * This is the entry point of gPXE from the point of view of the uIP
+ * protocol stack.  This function calls the appropriate methods from
+ * the connection's @tcp_operations table in order to process received
+ * data, transmit new data etc.
+ */
+void uip_tcp_appcall ( void ) {
+	struct tcp_connection *conn = *( ( void ** ) uip_conn->appstate );
+	struct tcp_operations *op = conn->tcp_op;
+
+	assert ( conn->tcp_op->closed != NULL );
+	assert ( conn->tcp_op->connected != NULL );
+	assert ( conn->tcp_op->acked != NULL );
+	assert ( conn->tcp_op->newdata != NULL );
+	assert ( conn->tcp_op->senddata != NULL );
+
+	if ( uip_aborted() && op->aborted ) /* optional method */
+		op->aborted ( conn );
+	if ( uip_timedout() && op->timedout ) /* optional method */
+		op->timedout ( conn );
+	if ( uip_closed() && op->closed ) /* optional method */
+		op->closed ( conn );
+	if ( uip_connected() )
+		op->connected ( conn );
+	if ( uip_acked() )
+		op->acked ( conn, uip_conn->len );
+	if ( uip_newdata() )
+		op->newdata ( conn, ( void * ) uip_appdata, uip_len );
+	if ( uip_rexmit() || uip_newdata() || uip_acked() ||
+	     uip_connected() || uip_poll() )
+		op->senddata ( conn );
+}
+
+/* Present here to allow everything to link.  Will go into separate
+ * udp.c file
+ */
+void uip_udp_appcall ( void ) {
+}
diff --git a/src/util/prototester.c b/src/util/prototester.c
index b4a5bc9a..f520d668 100644
--- a/src/util/prototester.c
+++ b/src/util/prototester.c
@@ -8,11 +8,11 @@
 #include <sys/un.h>
 #include <net/if.h>
 #include <net/ethernet.h>
-#include <netinet/in.h>
-#include <arpa/inet.h>
 #include <getopt.h>
 #include <assert.h>
 
+#include <gpxe/tcp.h>
+
 typedef int irq_action_t;
 
 struct nic {
@@ -68,14 +68,14 @@ static inline void free_netdevice ( struct nic *nic ) {
 	/* Do nothing */
 }
 
-static int netdev_poll ( int retrieve, void **data, size_t *len ) {
+int netdev_poll ( int retrieve, void **data, size_t *len ) {
 	int rc = static_nic.nic_op->poll ( &static_nic, retrieve );
 	*data = static_nic.packet;
 	*len = static_nic.packetlen;
 	return rc;
 }
 
-static void netdev_transmit ( const void *data, size_t len ) {
+void netdev_transmit ( const void *data, size_t len ) {
 	uint16_t type = ntohs ( *( ( uint16_t * ) ( data + 12 ) ) );
 	static_nic.nic_op->transmit ( &static_nic, data, type,
 				      len - ETH_HLEN,
@@ -245,137 +245,6 @@ static void hijack_disable ( struct hijack_device *hijack_dev ) {
 	close ( hijack->fd );
 }
 
-/*****************************************************************************
- *
- * uIP wrapper layer
- *
- */
-
-#include "../proto/uip/uip.h"
-#include "../proto/uip/uip_arp.h"
-
-struct tcp_connection;
-
-struct tcp_operations {
-	void ( * aborted ) ( struct tcp_connection *conn );
-	void ( * timedout ) ( struct tcp_connection *conn );
-	void ( * closed ) ( struct tcp_connection *conn );
-	void ( * connected ) ( struct tcp_connection *conn );
-	void ( * acked ) ( struct tcp_connection *conn, size_t len );
-	void ( * newdata ) ( struct tcp_connection *conn,
-			     void *data, size_t len );
-	void ( * senddata ) ( struct tcp_connection *conn );
-};
-
-struct tcp_connection {
-	struct sockaddr_in sin;
-	struct tcp_operations *tcp_op;
-};
-
-int tcp_connect ( struct tcp_connection *conn ) {
-	struct uip_conn *uip_conn;
-	u16_t ipaddr[2];
-
-	assert ( conn->sin.sin_addr.s_addr != 0 );
-	assert ( conn->sin.sin_port != 0 );
-	assert ( conn->tcp_op != NULL );
-	assert ( sizeof ( uip_conn->appstate ) == sizeof ( conn ) );
-
-	* ( ( uint32_t * ) ipaddr ) = conn->sin.sin_addr.s_addr;
-	uip_conn = uip_connect ( ipaddr, conn->sin.sin_port );
-	if ( ! uip_conn )
-		return -1;
-
-	*( ( void ** ) uip_conn->appstate ) = conn;
-	return 0;
-}
-
-void tcp_send ( struct tcp_connection *conn, const void *data,
-		       size_t len ) {
-	assert ( conn = *( ( void ** ) uip_conn->appstate ) );
-	uip_send ( ( void * ) data, len );
-}
-
-void tcp_close ( struct tcp_connection *conn ) {
-	assert ( conn = *( ( void ** ) uip_conn->appstate ) );
-	uip_close();
-}
-
-void uip_tcp_appcall ( void ) {
-	struct tcp_connection *conn = *( ( void ** ) uip_conn->appstate );
-	struct tcp_operations *op = conn->tcp_op;
-
-	assert ( conn->tcp_op->closed != NULL );
-	assert ( conn->tcp_op->connected != NULL );
-	assert ( conn->tcp_op->acked != NULL );
-	assert ( conn->tcp_op->newdata != NULL );
-	assert ( conn->tcp_op->senddata != NULL );
-
-	if ( uip_aborted() && op->aborted ) /* optional method */
-		op->aborted ( conn );
-	if ( uip_timedout() && op->timedout ) /* optional method */
-		op->timedout ( conn );
-	if ( uip_closed() && op->closed ) /* optional method */
-		op->closed ( conn );
-	if ( uip_connected() )
-		op->connected ( conn );
-	if ( uip_acked() )
-		op->acked ( conn, uip_conn->len );
-	if ( uip_newdata() )
-		op->newdata ( conn, ( void * ) uip_appdata, uip_len );
-	if ( uip_rexmit() || uip_newdata() || uip_acked() ||
-	     uip_connected() || uip_poll() )
-		op->senddata ( conn );
-}
-
-void uip_udp_appcall ( void ) {
-}
-
-static void init_tcpip ( void ) {
-	uip_init();
-	uip_arp_init();
-}
-
-#define UIP_HLEN ( 40 + UIP_LLH_LEN )
-
-static void uip_transmit ( void ) {
-	uip_arp_out();
-	if ( uip_len > UIP_HLEN ) {
-		memcpy ( uip_buf + UIP_HLEN, ( void * ) uip_appdata,
-			 uip_len - UIP_HLEN );
-	}
-	netdev_transmit ( uip_buf, uip_len );
-	uip_len = 0;
-}
-
-static void run_tcpip ( void ) {
-	void *data;
-	size_t len;
-	uint16_t type;
-	int i;
-	
-	if ( netdev_poll ( 1, &data, &len ) ) {
-		/* We have data */
-		memcpy ( uip_buf, data, len );
-		uip_len = len;
-		type = ntohs ( *( ( uint16_t * ) ( uip_buf + 12 ) ) );
-		if ( type == ETHERTYPE_ARP ) {
-			uip_arp_arpin();
-		} else {
-			uip_arp_ipin();
-			uip_input();
-		}
-		if ( uip_len > 0 )
-			uip_transmit();
-	} else {
-		for ( i = 0 ; i < UIP_CONNS ; i++ ) {
-			uip_periodic ( i );
-			if ( uip_len > 0 )
-				uip_transmit();
-		}
-	}
-}
-
 /*****************************************************************************
  *
  * "Hello world" protocol tester